History Main / ForgottenPhlebotinum

** Similar to the flamethrower instance from ''Series/{{Angel}}'' mentioned below, in the second season Buffy kills one random mook vampire by shoving a burning torch/brazier against its chest, which causes it to go up in flames like it was made of straw soaked in gasoline. Given how the series occasionally spiced up vampire-killing up with decapitation or holy water, it's a small wonder fire didn't come up more.

* Shows up in one of the many ''[[Comicbook/TheAvengers Avengers]]'' stories (the relaunch with Kurt Busiek). Justice, sidelined with a broken leg, goes on an ArchiveBinge and realizes that the best way to defeat an Adamantium robot on a homicidal rampage is with Antarctic (type B) Vibranium, a metal that somehow destroys any other metal within range when exposed to the air. Fortunately, the Avengers destroyed an AIM base with stocks of type B vibranium four or five issues previously; but in all the long history of Ultron's rampages, some of the finest minds (Stark, Pym et al) in the world never linked the "really tough metal" and "destroys metal on contact" dots together.

** Until someone points out it's an [[GeniusBonus old Nordic slang term]] for getting married. The Anglo-American equivalent would be "I used to be an adventurer like you, until I got latched to the old ball and chain."

LarryNiven is extremely critical of this trope, and coined Niven's Law, which states that once a technology or discovery has been introduced into a fictional setting, it must continue to exist in all chronologically later stories in that setting. The secret may be lost for a variety of reasons--society enters a dark age, the discoverer deliberately covers it up, or there really were NoPlansNoPrototypeNoBackup--but Niven would maintain that this smacks of lazy writing and is best avoided. At the very least, the precedent that such a machine is ''physically possible'' in the setting must be maintained--which makes it likely that older, HigherTechSpecies will possess it even if it never became prevalent in the protagonists' society.

** Civilization-wide Forgotten Phlebotinum can be somewhat justified if there are NoPlansNoPrototypeNoBackup, or if the civilization enters a Dark Age when lots of stuff is forgotten, but Niven's Law is still a good rule of thumb. At any event, once the technology has been proven to work once, then the natural laws which permitted it to happen must remain consistent from then on, regardless of whether the tech is ever rediscovered.

** A combination of a very short range[[hottip:* :best suited to stealthy, small vessels]], massive size[[hottip:* :anything but the largest vessels have to sacrifice too much of their other armament to mount one]], which requires a use that doesn't fit with the prevailing tactical ideology -- and a political climate[[hottip:* :its sponsor lost favour, and its debut performance generated massive bad feeling amongst the other powers-that-be]] which would prevent time and money being spent on fixing those problems? Not really surprising it never reappears.

* One of the most notorious parts of ''VideoGame/MegaMan'' lore: what happens to the weapons he obtains from the Robot Masters? In every game, he receives several invaluable weapons and tools, but by the time [[CardboardPrison Dr. Wily escapes from prison for what feels like the hundredth time]], Mega Man has discarded them. Among other amazing weapons, you'd think he'd keep something like the Ice Slasher [[hottip:*:''VideoGame/MegaMan1'' weapon capable of freezing enemies, even suspending them in ''mid-air''.]], Atomic Fire [[hottip:*: ''VideoGame/MegaMan2'' weapon, and likely the most powerful fire weapon in the Classic series when fully charged.]], Metal Blade [[hottip:*: Also from ''Mega Man 2''. Arguably one of the most useful weapons in the entire series. Could be considered a GameBreaker, as it can be used over 100 times before running out of energy, fired in any direction and is effective against numerous bosses and enemies.]], or the Flash Stopper [[hottip:*: Stops friggin' ''TIME'', man. It is the ''VideoGame/MegaMan4'' upgrade to ''Mega Man 2'''s Time Stopper, as the Flash Stopper allows you to shoot while enemies are frozen.]] on hand for when Wily predictably reappears, but no. Especially groan-worthy when you realize that he sometimes has to obtain these weapons for the second, third, fourth, or ''(rarely) FIFTH time'' in later games (such as the arcade and Game Boy titles).

* There are a number of things in ''LightNovel/ACertainMagicalIndex'' that only come up once and are discarded once Toma defeats them. The Level Upper program from ''Manga/ACertainScientificRailgun'', for example, is a noise file that increases a listener's power level before putting them in a coma, in which state they can be used as an organic computer for the controller of the network to make use of ''all'' their powers--this would be absolutely perfect for the Sisters, but it's never brought up. Of course, this is justified, since both the magic and science sides are very competitive even within their own fields, and refuse to share research any more than is strictly necessary. Has some elements of MisappliedPhlebotinum as well.

* Every once in awhile this will happen in ''Franchise/KamenRider'' due to the Heisei Series being more toyetic. However, one of the most notorious early examples comes from ''KamenRiderX''. In Episode 2, Jin Keisuke uses a two-barrel blowdart gun that manages to make short work of GOD minions AND stop the Kid Of The Week from being lynched. In spite of it looking like the coolest thing ever, it is never seen again.

* Chuck Sonnenburg of Website/SFDebris loves to call out ''Franchise/StarTrek'' for forgetting that the ship has shuttlecraft, and was stunned when ''Series/{{Firefly}}'' '''didn't''' (from his review of [[[[http://sfdebris.com/videos/firefly/firefly7.asp "Out of Gas").

** Bala, a technique used by Arrancar, is weaker than a Cero but 20 times faster... but apparently not so much weaker as to prevent Ulquiorra from blasting chunks into two Shinigami [[RedShirt Red Shirts]]. Despite this, the only Arrancar to consistently use it is [[DumbMuscle Yammy]]

!!Examples:

* The [[BigBad Evil Queen]] in ''Series/OnceUponATime'' has the ability, at least in the Enchanted Forest, to [[AndShowItToYou pull a person's heart out]] yet leave them not only alive, but subject to her will. It's implied or explicitly stated that she's done this many times, yet she has to send Snow White into the woods with the Woodsman to get him to cut her heart out mundanely, rather than doing the job herself and turning her hated step-daughter into a slave and puppet ruler.

!Examples:

-->-- ''AltText for Webcomic/DinosaurComics, [[http://www.qwantz.com/index.php?comic=1307 9/18/08]]''

!!Examples:

[[folder:{{Anime}} and {{Manga}}]]

[[folder:Film]]

[[folder:Live Action TV]]

[[folder:WebComics]]

* A rare villain example in ''WesternAnimation/TheNightmareBeforeChristmas'': Oogie Boogie has the ability to suck in everything like a gigantic vacuum, which is how he [[spoiler:recaptured Santa and Sally]]. He never thought to use this in his battle against Jack Skellington, though this is somewhat justified, as Oogie was trying to get ''away'' from Jack. [[JustEatGilligan Still could have ate him, though.]]

----

** Wolfram and Hart may not have been aware of it, and Wesley himself stated that wasn't really Angelus.

** The issue of the Adjoining Spell from the end of Season Four. Arguably the most powerful spell seen in the entire series, although with the drawback of [[spoiler:causing the spirit of the First Slayer to try to kill everyone involved in their dreams]]. It is never mentioned again.

*** Justified in that last time Jack did that, [[ChronicBackstabbingDisorder Wuya immediately betrayed him]] and tried to take over the world. Ultimately subverted in that Chase Young eventually used this exact method to resurrect Wuya.

* At the end of ''Film/StarTrekNemesis'', all the transporters on the Enterprise fail after Picard is beamed over. Their only recourse is to have Data ''jump'' over and use a never-before-seen one-person mini-transporter badge to get Picard back and then die with the enemy ship himself. Everyone seemed to forget ''the shuttles have their own independent transporters''.

* In the Franchise/StarTrekNovelVerse, the phase-cloak seems to go through this a lot. After its introduction (and successful use) in an episode of ''Series/StarTrekTheNextGeneration'', it's largely ignored by the books (as well as later TV series). A short story in a ''Literature/StarTrekNewFrontier'' anthology eventually suggested the prototype was destroyed soon after the episode. By the time of ''StarTrekTheGenesisWave'', the Romulans are making use of the technology again, or something very much like it, but then it drops off a second time, and when ''StarTrekTitan'' comes round no-one's using it. Finally, in the ''StarTrekTyphonPact'' series, we're explicitly told the Romulans have finally perfected it.