History ScrappyWeapon / TheBindingOfIsaac

** Originally, plot-relevant items[[note]]The Polaroid, The Negative, the Key Pieces, the Knife Pieces and Dad's Note[[/note]] were also affected by TMTRAINER, meaning your run was practically guaranteed to end early if you ever pick TMTRAINER up — this resulted in a [[UnintentionallyUnwinnable softlock]] in the pre-ascent version of Mausoleum/Gehenna, as there was no way to progress without picking up Dad's Note… which was glitched and unusable. [[WordOfGod Edmund]] later clarified this was [[GameBreakingBug a bug]], and to the relief of one too many, it was fixed as of the November 2021 update, meaning these items are now fortunately safe from the effects of TMTRAINER.

* The '''Birthright''' was formerly this. It's a shop item that provides a unique effect tailored to the character you're playing as. Most of these effects are incredibly useful, typically patching up a key weakness or improving on the character's strengths. The problem is that, formerly, [[ObviousBeta only about half of the characters in the game had an effect implemented]], and while the item can still spawn for said characters, picking it up does ''nothing''! For players who don't know the effects, it would be a complete toss-up as to whether it would be a godsend or a waste of 15 coins, while to those who did, it would feel like a waste of a trip to the shop when it showed up. As of the November 2021 update, however, every single character now has an effect attributed to them and most of them are incredibly useful.

* '''[[ThrowDownTheBomblet Bob's Brain]]''' and '''[[ActionBomb BBF]]'''. The former is an explosive projectile familiar that you can fire at enemies [[StatusInflictionAttack for poison damage]]. The latter is a friendly Boom Fly that bounces across the room, exploding on contact with an enemy. What makes them divisive is that they have a tendency to respawn as you're firing your tears in close-quarters; there's nothing worse than having them respawn and explode on top of an adjacent enemy, catching you in the blast. Sometimes, BBF can even damage you ''as soon as you enter a room!'' Bob's Brain, at least, [[BalanceBuff was toned down a bit]] in ''Afterbirth'', as it now can't be fired for a few seconds after it spawns or after you enter a room, preventing surprise explosions. Then ''Repentance'' came along and gave both items the ability to [[PowerUpLetdown "synergize"]] with Bomber Boy, which substantially increases their blast radius, and thus their ability to hurt you.

* On the other side of the spectrum is '''[[PsychoKnifeNut Mom's Knife]]''', one of the biggest {{Game Breaker}}s, but also considered by a few people to be [[BoringButPractical one of the dullest items in the game]]. The knife you can throw is extremely powerful at its longest range, dealing enough damage to do a number on even {{Final Boss}}es, especially if they're stationary (like Mega Satan). However, the knife is infamous for either not synergizingwell with other tear effects, or ''at all'', which tends to kill any powerful build you may have. As a result, some players (including seasoned veterans) often opt to skip this item, either due to its anti-synergistic potential, or in an attempt to make [[NintendoHard the difficulty of the game]] truly shine. Even those that will take Mom's Knife can find the item unwieldy at times, such as trying to fire diagonally but instead doing so horizontally[=/=]vertically due to the input being frame perfect. ''Repentance'' worked around this issue by making the input no longer require to be frame perfect.

* '''[[BeamSpam Technology 2]]''' is another very infamous example. Having a constant laser that fires while you do is a nice idea for an item, but the main problem is that it halves down your firing rate and, on top of it, cuts down your damage stat ''directly'' as well, and significantly so. The laser itself, much like Technology, has no knockback, which when combined with the massive damage reduction and the reduced rate of fire means you'll need to shoot down the enemy with the laser ''and'' the tear to make the damage count. ''Rebirth'' further emphasized its problems by making the laser itself deal even less damage, causing tanky enemies to [[DeathOfAThousandCuts take AGES to go down]] unless you happen to have good Damage. Finally, when used by Cain (or alongside items that make you fire tears only from the right eye, like Lead Pencil from ''Afterbirth†''), tears won't fire at all anymore, only firing the laser that deals pitiful damage. As a result, compared to the more traditional [[RayGun Technology]], Tech 2 is widely considered to be a huge downgrade. Additionally, ''Rebirth'' introduced Tech.5, a laser that has a random rate of fire but doesn't replace your main source of fire nor affect your stats, and has its own effects, which pushed Technology 2 even further downhill. Fortunately, ''Repentance'' [[RescuedFromTheScrappyHeap removed it from this category]] by making it no longer reduce your Damage stat, making the rate of fire downgrade much lower, granting the beam slight knockback (much like with other ''Tech'' items), and granting the regular Technology effect when used by Cain[=/=]with items that fire from the right eye, meaning that it's now much more worth a try.

* '''[[HolyBurnsEvil Holy Water]]''' is a familiar that activates when taking damage, but compared to other similar familiars, it breaks and merely spawns a small puddle of blue creep that deals some damage to enemies, similarly to the Lemon Mishap effect. Since enemies are still able to move around when they stand on the creep, the damage they'll take is scratch damage at best, especially during later chapters where enemies are tankier and faster (and from the Womb onward, you take a full heart of damage each time). Oh, and it can only be used once per room. This makes not only for a widely disliked item, but alongside some items like Breath of Life or Trisagion, it is one of the go-to examples when arguing about why the Devil Room item pool is better than the Angel Room item pool, even with the existence of other powerful items like [[GameBreaker Sacred Heart or Godhead]]. ''Repentance'' fortunately threw Holy Water a bone and [[AuthorsSavingThrow heavily reworked it]], firmly removing it from this category by making it a familiar that flies forward when Isaac shoots and breaks on contact with enemies, also making the creep petrify enemies and bosses to make them take the full brunt of the damage. It's now considered one of the best non-stat boosting Angel Room items, and some even argue for it being ''the'' best.

* '''[[ThrowDownTheBomblet Dr. Fetus]]''', of all items, became this in ''Rebirth''. A DifficultButAwesome tear modifier that can damage you if you're not careful, in the original, it was still seen as a borderline GameBreaker due to its tremendous damage output. In ''Rebirth'', however, Dr. Fetus bombs had the self-damage reduced ''and'' damage output massively reduced, meaning that it now fails to consistently OneHitKill many normal enemies and kills bosses ''very'' slowly. It did receive an increased fire rate, which theoretically makes Dr. Fetus an overall damage upgrade, but since bombs have a tendency to knock each other around — often into ''[[HoistByHisOwnPetard your face]]'' — it's still not worth picking it up. By comparison, fellow explosive attack Ipecac has the same self-damage, but deals much more damage to enemies. Fortunately, ''Afterbirth'' restored Dr. Fetus to its former glory, as well as adding tons of new synergies with that, and ''Repentance'' further buffed the item by making each bomb shot's explosions inflict no knockback to other bomb shots.

* The '''[[BulletTime Stop Watch]]''', which is frowned upon for either being too powerful or too weak of an item, depending on what version of the game you're playing. In ''Rebirth'', it is a huge GameBreaker which slows down enemies and projectiles for the entire game, which makes it become a complete cakewalk. In ''Afterbirth'', however, the item is this instead, as its slowdown effect not only lasts for only one room, but only activates if you take damage (though this can be worked around by using the Holy Mantle). ''Repentance'' restored it to its former glory by applying its slowdown effects to the entire run again, but much less powerfully than before, though with the caveat of synegizing with the actual slow {{status effect|s}}.

* '''[[Franchise/{{Pokemon}} Missing No.]]''' is another particularly infamous example. The item will reroll all of your items like the D4 and modify your stats, but that's not the bad part… that would be that, whether you want it or not, this will happen ''again'' at the start of each floor. This can turn any build you may have (be it a decent one or even a GameBreaker) prior to picking Missing No. up into a LuckBasedMission in which you'll hope the items granted to you don't make you underpowered or even worse, cause the run to be borderline unplayable. The item is also one of the few unable to be rerolled by an another reroll effect, so you'll have to deal with holding onto it. It is technically able to turn any bad run you may have into something much better, but then it'll just take that run away on the next floor. You're better off with the D4 or D100 to get ''controlled'' versions of these effects. Unlike many other items on this page, ''Repentance'' only made the item ''even worse'' due to the nerfs made to reroll effects, as while any items that are removed can be encountered again during the run, any transformations from items that grant them and any red heart containers you had from health upgrades will now be removed if you lose the items that granted them.
* '''[[BeatStillMyHeart Isaac's Heart]]''' is a risk-reward item that's far too light on reward. Your body no longer has a hurtbox, which sounds great… if it wasn't for the fact said hurtbox will now be following your back as a familiar that enemies will be 100% of the time aiming for. Knowing how the mechanics for familiars work (and as later infamously seen with characters like Lilith's Incubus), having a hitbox that trails behind you is not a good thing at all. It's especially terrible when it's not the first familiar on your line, as it makes the heart much harder to properly protect. It's because of these traits that players will almost always avoid it. Keyword being "almost" because, in spite of its negatives, the item does have [[SituationalSword a few situational positives]] that can lead to some {{Game Break|er}}ing combos that make infinite use of [[CastFromHitPoints red heart containers]], such as Blood Donation Machines or the IV Bag for [[EleventyZillion infinite money]], offering to to Demon Beggars until they pay out with an item, using the [[StatusBuff Razor Blade]] for infinite damage stacking, or using [[SmartBomb Blood Rights]] to damage everything in the room until it's empty of enemies. The heart familiar can also fortunately be sacrificed with the [[DealWithTheDevil Sacrificial Altar]] in ''Afterbirth†'' for a free item in return, and from the Devil Room item pool at that. Still, without a way to exploit Isaac's Heart to your benefit, do '''''not''''' ever think about touching that item pedestal containing the item.

* Whereas many of the "Bean" items are purposely bad, but accepted due to balance purposes, the same can't be said about the '''[[JokeItem Butter Bean]]'''. It's an active item that only has the effect of producing a small fart that can knock back some enemies. At least it recharges spontaneously, and in ''Afterbirth'' it can deflect bullets. ''Afterbirth†''made it so swapping it with another active item repeatedly can transform it into "Wait What?", an identical-looking bean that loses the fast recharge time in exchange for creating a circle of rock waves around Isaac; however, for whatever reason, the swapping effect was removed in ''Repentance'', although it also made knockback from the farts deal damage to enemies if they collide with obstacles, walls or other enemies. Still, considering that all this item does is a miserable fart, you'll still want to swap Butter Bean with another ''much'' better active item.

** ''Repentance'' gave the item a buff that allows it to be used in combat, by creating [[BoltOfDivineRetribution Bolts of Divine Retribution]] on contact with an enemy, but this buff didn't do anything to improve on its core problems. It wasn't until the 1.7.9 update when the item [[RescuedFromTheScrappyHeap got reworked]] by drastically reducing the time it takes for the invincibility to kick in, giving a visual cue when it's active, and granting it further offensive and defensive usage by summoning a cross of powerful holy beams and a shield on contact with enemies ''[[JustFrameBonus as the invincibility activates]]'', turning what was once one of the most underwhelming items into a DifficultButAwesome item.

* '''[[ChargedAttack Monstro's Lung]]''' replaces Isaac's tears with a charged shot that spews a cluster of 14 tears that fly out at varying distances, similar to Monstro's main attack. Like all charged tear modifiers, this makes you more vulnerable to fast-moving enemies or enemies that get up in your face, as there is no reliable way to push them back while charging. Where Monstro's Lung ''really'' falls flat though is the trade-off compared to other charged attacks like Brimstone and Tech X -- each tear only deals base damage, meaning that the spew's innacuracy makes it only effective when very close to enemies or facing particularly clustered groups. It also doesn't come with piercing to offset the downtime charging causes. The item does have a ton of cool and useful synergies, and it ''can'' [[MagikarpPower see great effect with damage/fire rate upgrades]], but without them, it's a risky pickup in the early game by itself in most cases.

* ''Afterbirth'' added a bunch of new transformations; of these, '''Conjoined''' stands out for being extremely divisive. After picking up three shooting familiars, Isaac grows two faces on his cheeks that fire tears along side him, at the cost of directly reducing his damage and tears, an effect no other items or transformations have; while the transformation is ''technically'' a significant increase in DPS, the stat downs it grants, despite being low enough to compensate on their own, tend to lower your overall DPS in front of you, which isn't desirable without enough damage/tears upgrades. The spread at which the tears fire is much wider than that of The Inner Eye, firing at 90° ala The Wiz (described above), so while it has the potential for better crowd control and some powerful synergies, it's not as effective against enemies right in front of you (not helped by the aforementioned stat reductions); this problem is more apparent on tight spaces. Though the transformation is rare (pre-''Repentance'', only seven familiars counted towards progress for the transformation), the familiars that compose it are some of the most underwhelming in the game[[note]]With Mongo Baby being the only exception due to its higher DPS and PowerCopying effects[[/note]], so chances are, if you have a bunch of familiars, you're losing on some of the stronger items, which is quite problematic in the early game (though [[MagikarpPower not so much in the late game]]). ''Repentance'' did make Conjoined easier to obtain by including a drastically higher amount of familiars that contribute to progress, many of which are much stronger[[note]]Such as Multidimensional Baby, Dry Baby, Seraphim, Sworn Protector, [[GameBreaker Incubus and Twisted Pair]] (the latter two of which synergize impeccably with Conjoined)[[/note]], which combined with the higher item count and the various changes to item pools makes the potential for getting the transformation easier; though this can potentially help in playing to the transformation's strengths, it still doesn't compensate for its other inherent problems. All in all, it's still a hot topic of debate to this day to whether Conjoined is worth looking for or not; some people argue that its crowd control, increase in DPS and synergy potential far outweigh the front DPS reduction, while others either couldn't care less for the extra shots or consider them a hindrance, while stating that the stat downs it grants are just a potential gut punch to a bad run.

* '''[[CriticalStatusBuff Dark Prince's Crown]]''' suffers from being extremely specific on the requirements needed to activate its effects. It grants a sizeable tears up, as well as a range and shot speed up if you're at one red heart… and ''{{exact|Words}}ly'' one red heart, since you'll lose the effect at either half a red heart or with no heart containers; this also means the item has ''[[PowerUpLetdown no effect]]'' on characters that can't gain red hearts, such as [[JokeCharacter Blue Baby]] or [[OneHitPointWonder The Lost]]. A bunch of other items already activate their effects at lower red heart requirements, such as The Polaroid/Negative, Whore of Babylon, Empty Vessel, etc., meaning that Dark Prince's Crown competes ''directly'' with these items, and can potentially prevent you from unlocking their more powerful effects, despite the noticeable increase in fire rate. It's especially disappointing if you can't manage to find soul/black hearts to offset the specific red heart requirement. Ironically, the only character it synergizes well with is Eve (since her own Whore of Babylon effect activates at one red heart or less instead of half a red heart).

* Bomb upgrades already tend to be hit or miss, but '''Fast Bombs''' is easily the worst of the bunch. It removes the cooldown on bomb placement and grant 7 bombs. Though certainly a fun concept, this effect is ''incredibly'' niche, making the extra bombs often more useful than the actual item (which, while two more than most bomb upgrades, is still less than Boom!'s +10). The only real use is the combination with Remote Detonator, which will allow you to quickly one-shot most bosses if you're willing to expend a bunch of bombs, but even that is merely faster than placing all the bombs manually. ''Repentance'' gave the item a much-needed buff, making bombs immune to each other's knockback, making the item drastically safer and less prone to [[HoistByHisOwnPetard launching bombs your way]]; it's still fairly underwhelming, though.

* '''[[BoltOfDivineRetribution Trisagion]]''' looks a lot like the equivalent to a "holy Brimstone" shot, but in reality has a lot to live up to. The light blasts you shoot pierce enemies but deal only 1/3 of your current damage per tick, and much like Technology, cause no knockback. With a high Shot Speed (a stat liked for its ability to reach enemies faster), it also becomes even weaker, as the blast of light will go through the enemy faster, dealing only scratch damage in the process. Only with a low Shot Speed (a ViolationOfCommonSense) does it become stronger, as the damage per tick is more constant, but even so, the items that reduce the Shot Speed (like Lost Contact, Godhead, or Sacred Heart) are so rare, and there are many more alternatives available, it's often not worth picking it up. And on top of that, [[ArsonMurderAndJaywalking it has a massive tendency to make the game lag like crazy]]. It's no surprise why the item gets the nickname of "Tri-BAD-ion" by some players. ''Repentance'', fortunately, buffed Trisagion through the introduction of Shot Speed Down pills, each blast now causes slight knockback, and the item now has a slew of synergies to go with it… including a "Scrappy Synergy" with Ipecac where the Ipecac-powered Trisagion blasts exploded immediately after you fired them, resulting in you taking unavoidable self-damage whenever you fired (and eventually finding yourself [[GameOver seeing Isaac's last will]]). Thankfully, the November 2021 update fixed the combo, and Trisagion has been less divisive since then.

** '''[[DashAttack Mars]]''' is also not bad, but it certainly feels unwieldy at times. Its effect is certainly excellent: by pressing a movement button twice, it grants you a dash attack that makes you invincible for its duration and deals great damage by itself; it makes Curse Rooms free of entry and also stacks with other items that deal contact damage (like the newly buffed Aries) while synergizing with others (like Kamikaze! and A Pony[=/=]White Pony). However, the way it activates has caused a problem too many by activating it when one doesn't want to, which when combined with nearby sources of damage can lead to accidental self-damage and, in the worst of cases, [[YetAnotherStupidDeath an accidental death]] through little fault of your own. This becomes a bigger problem if your computer starts to lag, as the activation window for Mars becomes much wider due to the slowdown. And the biggest problem of all is that Mars does not give ''any'' additional invincibility frames after the dash attack finishes, which leads DIRECTLY into the problems stated above.
** When you think of '''Jupiter''', the first thing you'll think of is the [[Myth/ClassicalMythology Roman god of Thunder]] and [[UsefulNotes/Jupiter the gas giant of a planet in the Solar System]]… but not of a "gas giant" in [[ToiletHumor the literal sense]]. The item is a sizeable speed downgrade that forces you to stay still to build speed and, as soon as you walk, release it in a burst of {{fart|illery}}s. Not only is its effect mediocre at best, it forces you to play the game differently without offering much reward in return and, to boot, [[ArsonMurderAndJaywalking you're gonna have to hear the sounds of farts constantly]] and the item comes with [[{{Gonk}} one of the ugliest costumes in the game]]. It ''does'' provide immunity to all forms of Poison gas damage, but that is [[GuideDangIt not even hinted in the game at all]]. Its only upside is that the item does become more useful by picking up speed upgrades. Otherwise, compared to most several of the new Planetarium items (even Venus and Mars), Jupiter has quickly managed to get on people's nerves.

* '''[[ThrowDownTheBomblet Bob's Brain]]''' and '''[[ActionBomb BBF]]'''. The former is an explosive projectile familiar that you can fire at enemies [[StatusInflictionAttack for poison damage]]. The latter is a friendly Boom Fly that bounces across the room, exploding on contact with an enemy. What makes them divisive is that they have a tendency to respawn as you're firing your tears in close-quarters; there's nothing worse than having them respawn and explode on top of an adjacent enemy, catching you in the blast. Sometimes, BBF can even damage you ''as soon as you enter a room!'' Bob's Brain, at least, [[BalanceBuff was toned down a bit]] in ''Afterbirth'', as it now can't be fired for a few seconds after it spawns or after you enter a room, preventing surprise explosions. Then ''Repentance'' came along and gave BBF the ability to [[PowerUpLetdown "synergize"]] with Bomber Boy, which substantially increases her blast radius, and thus her ability to hurt you.

Generally speaking, most passive items that cause [[StuffBlowingUp explosions]] that you can't control are looked down upon by the community, as their blast radius can easily damage you. As such, picking up Host Hat or Pyromaniac to NoSell the explosions from these items is recommended:
* '''[[ThrowDownTheBomblet Bob's Brain]]''' and '''[[ActionBomb BBF]]'''. The former is an explosive projectile familiar that you can fire at enemies [[StatusInflictionAttack for poison damage]]. The latter is a friendly Boom Fly that bounces across the room, exploding on contact with an enemy. What makes them divisive is that they have a tendency to respawn as you're firing your tears in close-quarters; there's nothing worse than having them respawn and explode on top of an adjacent enemy, catching you in the blast. Sometimes, BBF can even damage you ''as soon as you enter a room!'' Bob's Brain, at least, [[AuthorsSavingThrow was toned down a bit]] in ''Afterbirth'', as it now can't be fired for a few seconds after it spawns or after you enter a room, preventing surprise explosions. Then ''Repentance'' came along and gave BBF the ability to [[PowerUpLetdown "synergize"]] with Bomber Boy, which substantially increases her blast radius, and thus her ability to hurt you.

* '''[[PlayingWithFire Fire Mind]]''' allows you to shoot tears that [[StatusInflictionAttack inflict]] burn DamageOverTime to enemies… but each tear has a chance to explode on contact with an enemy, with said explosion having a generous blast radius — not unlike that of Ipecac — but dealing pitiful damage to enemies. It completely ruins your primary attack's use for close-quarters combat, only allowing for hit-and-run combat. And even then, there are some enemies like Globins that [[NoSenseOfPersonalSpace love to be in your face]], making avoiding damage during hit-and-run tactics ''very'' hard. The worst part? The chance for explosions [[ScrappyMechanic scales with your Luck stat]], so the more luck you have, the more explosions you create. At least the resulting explosion deals less damage to you than that of a regular bomb, and ''Repentance'' made the explosion size smaller. Picking up certain tear modifiers, however, eliminates the explosion but leaves the fire damage, like [[BreathWeapon Brimstone]], Mom's Knife, or [[RayGun Technology]]. It is also a non-issue for Tainted Lilith in ''Repentance'', since her tears are fired from a distance via Gello.

* '''[[RandomEffectSpell 3 Dollar Bill, Fruit Cake, and Playdough Cookie]]''' have also won quite the amount of detractors as well because of their tendency to proc explosive effects that one wouldn't like to find — all three can roll Fire Mind, while Fruit Cake can also roll Ipecac. It is entirely possible for a run to [[GameOver end]] by picking up Fruit Cake and having it roll Ipecac [[FinaglesLaw at the worst possible time]]. Therefore, Fruit Cake is the worst item in this category.

* '''[[HorsemenOfTheApocalypse 7 Seals]]''' has its issue where its randomness and the effects of each of the little Harbingers can make it somewhat unreliable, but one of the item's main problems is the War transformation. The locusts[[note]]which are colored flies with different effects depending on the current harbinger[[/note]] he spawns (red locusts) are highly damaging, but can be easily turned against you due to the fact they have the same blast radius and damage as a bomb. Simply put, much like BBF, the red locusts can damage you whenever you enter a room whether you want it or not, making it a prime reason why this item is looked down on. And if the game is feeling {{spiteful|AI}}, War may be the most common Harbinger 7 Seals will roll, causing red locusts to spawn over and over. Of course, everything that applies to this item also applies to the '''[[ActionBomb Locust of War]]''' trinket. Thankfully, ''Repentance'' [[AuthorsSavingThrow made the blast radius of red locusts much smaller]], and while this does make them less effective at crowd control, it's a small price to pay when it means they're no longer blowing up in your face all the time.
* '''IBS''', similar to Tainted ???'s gameplay gimmick, has a chance to give you one of several throwable poops or otherwise poop-themed effects whenever you damage an enemy. ''Unlike'' Tainted ???, you can't control when to use these poops — they activate on their own, indicated by Isaac's sprite flashing red, and deploy automatically once you stop firing. This is bad enough on its own, since you can't shoot when you're holding a poop, but it can also give you an ''active'' throwable bomb or the effects of an Explosive Diarrhea pill at complete random. Even green poops, ordinarily one of the more useful kinds due to the poison clouds they emit, can be a liability. If the RNG decides to give you fire poop while you're standing near them (or one of their gas clouds)… BOOM!

* '''[[BoomerangComeback My Reflection]]''' is a particularly infamous one, as it just makes your tears boomerang around wildly, cutting your range and making it hard to aim. Some combinations using it will screw you even harder, such as combining it with Ipecac or Bob's Rotten Head, causing your explosive projectiles to [[HoistByHisOwnPetard boomerang right back at you]]. Even worse is that the Suicide King challenge in ''Rebirth'' sticks you with the My Reflection + Ipecac combo [[StopHittingYourself for the entire run]]. The item did receive in update 1.7.9 an (admittedly significant) improvement on damage at the cost of a luck nerf, but don't let this change make it appetizing as an early pick, as the item's core problems still prevent it from being a remotely good pick, especially considering the amount of negative interactions it has with most of the other items in the game. It works surprisingly well with Azazel, however, as it's one of the few items that increases his otherwise short range.

* '''[[SmartBomb The Necronomicon]]''' isn't disliked so much as it is just ignored due to there being many more alternatives available. It's a 6-room charge item that deals 40 damage to every single enemy in the room, meaning it can kill tender enemies and heavily soften the tankier ones, so it's a Death tarot card on command and can save a lot of time in dealing with hordes of enemies, especially early-game. Similarly to The Bible, however, its 6-room charge makes it pretty underwhelming. Even a cheaper alternative from ''Rebirth'' is Blank Card + Death, which takes 4 rooms to charge. ''Repentance'' gave the item some love, though, as not only was its charge time reduced from 6 to 4 rooms (much like The Bible), but it now synergizes with both the newly buffed Missing Page trinket and the Missing Page 2 passive item, since both now universally double the Necronomicon effect for 80 damage instead of 40, and can even stack with each other for ''[[ThereIsNoKillLikeOverkill 120 damage]]'', easily decimating ''everything'' in the room and taking a large chunk off of some bosses. But even then, due to [[RandomNumberGod RNG]], you will probably not find all three of those items in a single run. The Necronomicon is an ''active'' item, which hogs your active item slot, the Missing Page is a trinket that takes up your trinket slot unless you gulp/smelt it, and the Missing Page 2, while a Passive Item, is incredibly underwhelming by itself.
* On the other side of the spectrum is '''Mom's Knife''', one of the biggest {{Game Breaker}}s, but also considered by a few people to be one of the dullest items in the game. The knife you can throw is extremely powerful at its longest range, dealing enough damage to do a number on even {{Final Boss}}es, especially if they're stationary (like Mega Satan). Moreover, in the original game, the knife did not synergize well with other tear effects. As a result, some players (including seasoned veterans) often opt to skip this item, in an attempt to make [[NintendoHard the difficulty of the game]] truly shine. Even those that will take Mom's Knife can find the item unwieldy at times, such as trying to fire diagonally but instead doing so horizontally[=/=]vertically due to the input being frame perfect. ''Repentance'' worked around this issue by making the input no longer require to be frame perfect.

* '''[[ThrowDownTheBomblet Dr. Fetus]]''' became this in ''Rebirth''. In the original, it was seen as a borderline GameBreaker due to its tremendous damage output, but also carried a [[DifficultButAwesome high chance of damaging yourself with one of your explosions]]. In ''Rebirth'', Dr. Fetus bombs had the self-damage reduced, but also suffered a massive damage drop, meaning that it now fails to consistently OneHitKill many normal enemies and kills bosses ''very'' slowly. It did receive an increased fire rate, which theoretically makes Dr. Fetus an overall damage upgrade, but since bombs have a tendency to knock each other around — often into ''[[HoistByHisOwnPetard your face]]'' — it's still not worth picking it up. It doesn't help that fellow explosive attack Ipecac has the same self-damage, but deals much more damage to enemies. Fortunately, ''Afterbirth'' restored Dr. Fetus to its former glory, as well as adding tons of new synergies with that. ''Repentance'' further buffed the item by making their explosions inflict no knockback to other bombs shot.
* '''[[BlessedWithSuck Cursed Eye]]'''. While the quadruple charge shot is nice, if you are hit while charging the shot (but not while holding a full charge), you will be teleported to a random room. This makes fighting [[ThatOneBoss the more difficult bosses]] ''even more problematic'', as even one mistake can warp you away and ruin all of your progress. Fortunately, this drawback can be worked around by picking up the Black Candle item (which eliminates the teleporting effect and leaves you with the quad shot) or a different tear modifier (like Brimstone). The teleporting effect can even be beneficial in some circumstances — most notably, allowing you to take a free item from the Boss Rush room. ''Repentance'' also buffed the item by making the full charge become a ''quintuple'' shot, and added a few more synergies with the item, such as with Technology. On the other hand though, woe unto you if you're playing as [[LuckBasedMission Tainted Eden]] and you reroll into Cursed Eye without realizing it and get teleported out of one of the [[MarathonBoss Marathon Bosses]] such as Hush or Delirium.
* The '''[[BulletTime Stop Watch]]''', which is frowned upon for either being too powerful or too weak of an item, depending on what version of the game you're playing. In ''Rebirth'', it is a huge GameBreaker which slows down enemies and projectiles for the entire game, which makes it become a complete cakewalk. In ''Afterbirth'', however, the slowdown effect not only lasts one room, but only activates if you take damage (though this can be worked around by using the Holy Mantle). ''Repentance'' gave it a buff to apply its slowdown effects to the entire run again, but much less powerfully than before.

* Picking up '''[[Franchise/{{Pokemon}} Missing No.]]''' will reroll all of your items like the D4 and modify your stats. That's not the bad part. The bad part is that, whether you want it or not, this will happen ''again'' at the start of each floor. This can turn any build you may have (be it a decent one or even a GameBreaker) prior to picking Missing No. up into a LuckBasedMission in which you'll hope the items granted to you don't make you underpowered or even worse, cause the run to be borderline unplayable. The item is also one of the few unable to be rerolled by an another reroll effect, so you'll have to deal with holding onto it. It is technically able to turn any bad run you may have into something much better, but then it'll just take that run away on the next floor. You're better off with the D4 or D100 to get a ''controlled'' version of this effect. Unlike many other items on this page, ''Repentance'' only made the item ''even worse'' due to the nerfs made to reroll effects, as while any items that are removed can be encountered again during the run, any transformations from items that grant them and any red heart containers you had from health upgrades will now be removed if you lose the items that granted them.
* '''Isaac's Heart''' is a risk-reward item that's far too light on reward. Your body no longer has a hurtbox, which sounds great… if it wasn't for the fact said hurtbox will now be following your back as a familiar. One that enemies will be 100% of the time aiming for. Knowing how the mechanics for familiars work (and as later infamously seen with characters like Lilith's Incubus), having a hitbox that trails behind you is not a good thing at all. It's especially terrible when it's not the first familiar on your line, as it makes the heart much harder to properly protect. It's because of these traits that players will almost always avoid it. Keyword being "almost" because, in spite of its negatives, the item does have a few situational positives that can lead to some {{Game Break|er}}ing combos that make infinite use of [[CastFromHitPoints red heart containers]], such as Blood Donation Machines or the IV Bag for [[EleventyZillion infinite money]], offering to to Demon Beggars until they pay out with an item, using the [[StatusBuff Razor Blade]] for infinite damage stacking, or using [[SmartBomb Blood Rights]] to damage everything in the room until it's empty of enemies. The heart familiar can also fortunately be sacrificed with the [[DealWithTheDevil Sacrificial Altar]] in ''Afterbirth†'' for a free item in return. Still, without a way to exploit Isaac's Heart to your benefit, do '''''not''''' ever think about touching that item pedestal containing the item.
** ''Repentance'' brought a mix of buffs and nerfs to the item. The great? The heart will actively position itself opposite of where you shoot, it now has a ChargedAttack where it will stomp the floor to push enemies and bullets aside and release a ring of shots to protect itself, and your body will also deal contact damage to enemies. The egregious? Red heart containers are now depleted despite the body invincibility, meaning '''''every, single, game break,''''' with this item, was removed. And Sacrificial Altar will also no longer sacrifice the heart. All of this, while it makes it easier to protect the heart, it now gives the item no incentive to be picked up ''ever'', making it even more of a {{joke|Item}}.
* Whereas many of the "Bean" items are purposely bad, but accepted due to balance purposes, the same can't be said about the '''[[JokeItem Butter Bean]]'''. It's an active item that only has the effect of producing a small fart that can knock back some enemies. At least it recharges spontaneously, and in ''Afterbirth'' it can deflect bullets. ''Afterbirth†'' sort of removed it from this category, as swapping it with another item repeatedly can transform it into "Wait What?", an identical-looking bean that loses the fast recharge time in exchange for creating a circle of rock waves around Isaac. For whatever reason, the swapping effect was removed in ''Repentance'', although it also made knockback from the farts deal damage to enemies if they collide with obstacles, walls or other enemies. Still, considering that all this item does is a miserable fart, you'll still want to swap Butter Bean with another ''much'' better active item.
* '''Breath of Life''' was one of the go-to examples when arguing about why the Devil Room item pool far eclipses the Angel Room item pool. It's an active item that is used by holding the activate button, depleting the charge bar to zero to give you [[InvincibilityPowerUp a second of invincibility]]. However, the item has several downsides: first, if the button is left pressed for too long while you're invincible, you'll start to take damage instead of negating it. Second, after usage regardless of whether it was successful or not, the charge bar must hit max charge for the item to be used again. Its invincibility period has its uses, but they're extremely situational and invincibility periods are better done by other items anyways, like Book of Shadows or The Gamekid. Not to mention, the fact Breath of Life is found by skipping in a Devil Deal and hoping for the next room to be an Angel Room that could potentially reward more, only to find this item instead of a more useful one, is a huge negative.

* '''[[DeathOfAThousandCuts Soy Milk]]''', which is in roughly the same boat as Tiny Planet. At the cost of slashing 80% of your damage and tear size, it ''massively'' boosts the firing rate of your tears, to the point that a starting Isaac with Soy Milk has enough of a fire rate to shoot 30 tears per second. Unfortunately, the game has a hardcoded limit of ''15'' tears per second, meaning that while it's technically a bit more [=DPS=] than your default tears, that's only if you make ''every shot count''. Given the tears' knockback, the game's enemies and their erratic movement patterns, making all your tiny tears hit their mark so the damage output is at least decent is a huge pain in the neck — the [=DPS=] is so poor, all bosses become {{Marathon Boss}}es, and even ''[[TheGoomba flies]]'' take a lot more shots before they're down. And to add insult to injury, it's a special item in ''Rebirth'', so once you see it, your chances of a ''really'' good item in your current run fall dramatically! Only once you gain a '''lot''' of Damage ups or synergize Soy Milk with other certain items does it become a GameBreaker, due to its high firing rate carrying over. Fortunately, in ''Afterbirth'', Soy Milk is no longer a special item, meaning that it no longer interferes with your ability to get really good items just by showing up. As of ''Repentance'', the tears' knockback was also reduced dramatically (allowing tears to hit their target more frequently), the tear cap is no longer hardcoded at 15 per second, items that increase rate of fire ''affect'' Soy Milk's fire rate (which combines well with the previous change), a good number of items gained ''synergies'' with it, and there's finally the possibility of getting [[GameBreaker Rock Bottom]] alongside it, which prevents the damage reduction while keeping the increased rate of fire.
* '''Monstro's Lung''' replaces Isaac's tears with a charged shot that spews a cluster of 14 tears that fly out at varying distances, similar to Monstro's main attack. Like all charged tear modifiers, this makes you considerably more vulnerable to fast-moving enemies or enemies that get up in your face, as there is no reliable way to push them back while charging. Where Monstro's Lung ''really'' falls flat though is the trade-off, which is much worse than other charged attacks like Brimstone and Tech X. Each tear only deals base damage, meaning that the massive inaccuracy of the spew makes it only effective when very close to enemies or facing particularly clustered groups. It also doesn't come with piercing to offset the downtime charging causes. By itself, Monstro's Lung is a DPS downgrade in most cases, making it a risky pickup in the early game. The item does have a tonne of cool and useful synergies, but without them it's better off avoided.

* '''The Wiz''' doubles your rate of fire at the cost of sticking you with the "R U A Wizard" pill effect for the rest of the run, forcing you to shoot diagonally. Given that the game is based around being able to shoot in the cardinal directions, meaning that "R U A Wizard" is generally considered a negative effect, it's not a popular item at all. A few items can work around it though, most notably Tractor Beam, but ''good luck'' getting that combo ''at all''.
* '''[[HeelFaceTurn Betrayal]]''' and '''My Shadow''' are nothing more than small fishes that exist in a huge pond, that pond being the Devil Room item pool. [[CastFromHitPoints Upon hit]], enemies become charmed and attack each other rather than you, or are inflicted fear and you summon flunkies that deal damage to them but are destroyed easily, respectively. Not only are the effects incredibly lackluster, but since they activate by taking damage, you're better off with rerolling them or picking up any other item you may find in the room. Both items got buffed quite intensely in update 1.7.9 of ''Repentance'' by reworking them to no longer be on-hit effects, but rather having unique effects to each other[[note]]'''Betrayal''' now allows enemy projectiles to damage other enemies and cause them to attack each other, while '''My Shadow''' now functions similarly to Shade and creates the flunkies when they step in the shadow that follows you.[[/note]], removing them for some from this status.

* ''Afterbirth'' added a bunch of new transformations, but '''Conjoined''' is… dubiously useful. After picking up three shooting familiars, Isaac grows two faces on his cheeks that fire tears along side him. Great! Unfortunately, it also comes with a sizable damage down. The faces also fire diagonally like The Wiz, making them near-worthless for actually hitting anything. If you have a bunch of familiars, odds are your stats aren't very good to begin with, and Conjoined is just the gut punch to a bad run. ''Repentance'' also arguably made this even worse, since it added tonnes of new familiars into the Conjoined pool, making the transformation much more likely to get. On the bright side, it does make for some interesting synergies, and if you have enough damage upgrades, the damage down is not as impactful as it probably would have been without them.

* '''[[OneHitKill Plan C]]'''. It kills every enemy and boss in the game in a single hit... followed by [[PressXToDie killing you 3 seconds later]]. It's a SmartBomb with barely any of the "smart" factor in it, as it absolutely requires you to have an extra life in order to make the most use out of it. Its extreme damage output is also offset by bosses with multiple phases to their fights, meaning bosses like Hush or Mega Satan will not survive the first hit but will be ready for Round 2 while you simply [[YetAnotherStupidDeath die]]; thus, using the item in their second phase is the next best thing. Furthermore, using it on Delirium will cause you to die first because of its death animation taking so long to finish. It doesn't help that, while it's only likely to appear 1 time out of 5 in an item pool, it can be found in a total of '''8 item pools''' in the game [[note]]Curse Rooms (in both regular and Greed modes), Devil Beggars, Devil Rooms, Red Chests, Shops (in both regular and Greed modes) and Ultra Secret Rooms[[/note]], making it surprisingly more common than one would imagine despite its lowered item weight.
* The '''[[JokeItem Dataminer]]''' {{invoke|d Trope}}s this without much fanfare, due to being an item put in the game as merely [[TakeThatAudience a jab at the]] {{Content Leak}}ers that infamously datamined ''Rebirth''. It's a 4-room charge item that merely flips enemy sprites and grants random tear effects, while increasing one of Isaac's stats and decreasing another. Not only are its effects egregious, they are also reliant on the RandomNumberGod and fighting enemies becomes wonky. Oh, and [[ArsonMurderAndJaywalking it distorts the level's music, too]].
* The '''[[TheGambler Crooked Penny]]''' is another 4-room charge that works like a multiple-use Diplopia… but has a catch. The item's description, "50/50", is ExactlyWhatItSaysOnTheTin: it either duplicates items (even those that need to be bought) 50% of the time, or it fails to do so 50% of the time and instead removes every collectible in the room and spawns a measly penny. Half of the time you'll be happy and with your hands full, while the other half you'll be empty handed and cursing the RandomNumberGod for not allowing you to duplicate a GameBreaker like Brimstone. And knowing the game's AI tendency to [[SpitefulAI troll the player into oblivion]]… yeah. Overall, this amounts to one of the most divisive items in the entire game.

* Bomb upgrades already tend to be hit or miss, but '''Fast Bombs''' is easily the worst of the bunch. All it does is remove the cooldown on bomb placement and grant 7 bombs. The effect is ''incredibly'' niche, making the extra bombs often more useful than the actual item (which, while two more than most bomb upgrades, is still less than Boom!'s +10). The only real use is the combination with Remote Detonator, which will allow you to quickly one-shot most bosses if you're willing to expend a bunch of bombs, but even that's just... slightly faster than placing all the bombs manually. ''Repentance'' gave the item a much-needed buff and made Fast Bombs immune to each other's knockback, letting you use the Remote Detonator combo without needing Remote Detonator. It's still fairly underwhelming, however.
* '''Lacryphagy''' is rather divisive as well. Tears will quickly decelerate and become capable of absorbing other tears, causing them to grow until they burst into tears. While the main tear also deals the combined damage of each tear that fed it, the burst tears only deal half damage. What's more, not only must you pay attention to the enemies in the current room, but you are also forced to pay attention to how large the tear has become before it bursts. The item also has a tendency to not synergize with other tear modifiers as well. It's likely because of this that ''Repentance'' gave the item's synergy potential a massive buff, as items like Brimstone or Technology now synergize with it.
* '''[[BoltOfDivineRetribution Trisagion]]''' looks a lot like the equivalent to a "holy Brimstone" shot, but in reality has a lot to live up to. The light blasts you shoot pierce enemies but are horrendously weak, dealing 1/3 of your current damage per tick, and much like Technology, cause no knockback. With a high Shot Speed (a stat liked for its ability to reach enemies faster), it also becomes even weaker, as the blast of light will go through the enemy while dealing only scratch damage. Only with a low Shot Speed (a ViolationOfCommonSense) does it become stronger, as the damage per tick is more constant, but even so, the items that reduce the Shot Speed (like Lost Contact, Godhead, or Sacred Heart) are so rare, and there are many more alternatives available, it's often not worth picking it up. And on top of that, [[ArsonMurderAndJaywalking it has a massive tendency to make the game lag like crazy]]. It's no surprise why the item gets the nickname of "Tri-BAD-ion" by some players. ''Repentance'' buffed Trisagion by giving the blasts slight knockback and introducing a slew of synergies to go with it... including a "Scrappy Synergy" with Ipecac where the Ipecac-powered Trisagion blasts exploded immediately after you fired them, resulting in you taking unavoidable self-damage whenever you fired (and eventually finding yourself [[GameOver seeing Isaac's last will]]). Thankfully, the November 2021 update fixed the combo.

* '''[[SwordOfDamocles Damocles]]''' is one of the riskiest items in the game: on use it spawns a sword above you and causes all natural item pedestals to spawn a free second item beside them (not including items for sale or in chests); the catch is that upon taking damage from an enemy, the sword gains a chance to fall and [[OneHitKill insta-kill you]] at any moment [[JumpScare without warning]]. This creates a SadisticChoice -- Do you use the sword and try to play perfect from that moment on, or do you pass up on it and miss out on the free items? For most players it's the latter choice, given that it's extremely difficult to do a NoDamageRun and the upside is meaningless when you could lose your winning streak at total random. Extra lives can circumvent the insta-kill to a degree, although the item's positive effect will also disappear once the sword falls. At least Damocles is one of the absolute best items for [[OneHitpointWonder The Lost and Tainted Lost]], since they usually can't take damage anyway, and for Lazarus who gets an extra life per floor, should he die.

** When you think of '''Jupiter''', the first thing you'll think of is the [[Myth/ClassicalMythology Roman god of Thunder]] and the gas giant of a planet in the Solar System… but not of a "gas giant" in [[ToiletHumor the literal sense]]. Jupiter is a sizeable speed downgrade that forces you to stay still to build speed and, as soon as you walk, release it in a burst of {{fart|illery}}s. Not only is its effect mediocre at best, it forces you to play the game differently without offering much reward in return and, to boot, [[ArsonMurderAndJaywalking you're gonna have to hear the sounds of farts constantly]] and the item comes with [[{{Gonk}} one of the ugliest costumes in the game]]. Its only upside is that the item does become more useful by picking up speed upgrades. Otherwise, compared to most several of the new Planetarium items (even Venus and Mars), Jupiter has quickly managed to get on people's nerves. At least it provides immunity to all forms of Poison gas damage, but that is [[GuideDangIt not even hinted in the game at all]].
* The '''Birthright''' was formerly this. It's a shop item that provides a unique effect tailored to the character you're playing as. Most of these effects are incredibly useful, typically patching up a key weakness or improving on the character's strengths. The problem is that formerly, [[ObviousBeta only about half of the characters in the game had an effect implemented]], and while the item can still spawn for said characters, picking it up does ''nothing''! This means that for players who don't know the effects, it would be a complete toss-up as to whether it would be a godsend or a waste of 15 coins, while to those who did, it still felt like a waste of a trip to the shop when it showed up for a character it doesn't work on. As of the November 2021 update, however, every single character now has an effect attributed to them and most of them are incredibly useful.
** ...that is, unless you're playing Tainted Jacob, as from the same update onward, picking Birthright up will cause Dark Esau to [[FromBadToWorse spawn another clone of himself that will also charge at you]]. Despite the significant buffs Tainted Jacob received in the same update, if you thought juggling an angry soul trying to kill you was enough, now try juggling ''two''! On the other hand, [[DifficultButAwesome if you decide to face the risks and play to the item's strengths]], both souls charging at you can make facing hordes of enemies or certain bosses easier, since [[ThereIsNoKillLikeOverkill their huge contact damage is]] ''[[ThereIsNoKillLikeOverkill doubled]]''.

* '''[[Franchise/{{Pokemon}} TMTRAINER]]''' invokes the concept of GameBreakingBug to a degree never ever seen before. Picking it up seemingly does nothing… until you find an item. The items you will find in the run are completely glitched, and become [[RandomEffectSpell random combinations of 2-3 item effects, alongside randomly activating based on certain events (room clearing, killing an enemy, taking damage), and either being active or passive items]]. You may probably guess where the item is going, and yes, it is perfectly and completely capable of activating any undesirable effect, including from the ones in this page, from self-damage by using the item, to summoning Damocles' sword ready to kill you from the first screw-up, to outright [[YetAnotherStupidDeath dying ala Plan C]] after killing an enemy. This item also stars in a hidden challenge that is essential for getting OneHundredPercentCompletion, meaning you'll at least get a taste of just how chaotic it can be. [[SarcasmMode Have fun!]]

* ''Afterbirth'' added a bunch of new transformations, but '''Conjoined''' is… dubiously useful. After picking up three shooting familiars, Isaac grows two faces on his cheeks that fire tears along side him. Great! Unfortunately, it also comes with a sizable damage down. The faces also fire diagonally like The Wiz, making them near-worthless for actually hitting anything. If you have a bunch of familiars, odds are your stats aren't very good to begin with, and Conjoined is just the gut punch to a bad run. ''Repentance'' also arguably made this even worse, since it added tonnes of new familiars into the Conjoined pool, making the transformation much more likely to get. On the bright side, it does make for some interesting synergies, and if you have enough damage upgrades, the damage down is not as impactful as it probably would have been without them.

* '''[[ThrowDownTheBomblet Bob's Brain]]''' and '''[[ActionBomb BBF]]'''. The former is an explosive projectile familiar that you can fire at enemies [[StatusInflictionAttack for poison damage]]. The latter is a friendly Boom Fly that bounces across the room, exploding on contact with an enemy. What makes them divisive is that they have a tendency to respawn as you're firing your tears in close-quarters; there's nothing worse than having them respawn and explode on top of an adjacent enemy, catching you in the blast. Sometimes, BBF can even damage you ''as soon as you enter a room!'' Bob's Brain, at least, [[AuthorsSavingThrow was toned down a bit]] in ''Afterbirth'', as it now can't be fired for a few seconds after it spawns or after you enter a room, preventing surprise explosions.