Tauros used Hyper Beamnote A Normal-type attack! It doesn't affect Gengarnote A Ghost-type Pokémon, who are immune to Normal-type attacks...
Abilities:
Levitate, which makes the Pokémon immune to Ground-type attacks.
A couple of Pokémon have an ability called Mold Breaker (or its variations Turboblaze or Teravolt), which essentially lets them ignore the defensive effects of their target's ability and damage them anyway (for example, something with Levitate, like Rotom, can be hit by Earthquake).
Bibarel and Quagsire's Unaware, which lets them ignore all stat changes in opponents (except for Speed, as that would be mechanically problematic in group battles). Unless the opponent has the aforementioned Mold Breaker, in which case, they will No Sell your No Sell.
Solgaleo and Lunala's abilities, Full Metal Body and Shadow Shield, No-Sell abilities like Mold Breaker. The former is otherwise functionally identical to the aforementioned Clear Body, making it a No-Sell that can't be No Sold.
Rayquaza's Air Lock (or its variation, Cloud Nine) ability, which negates all weather effects caused by abilities or attacks.
Clear Body prevents negative stat changes inflicted by the opponent.
Soundproof (and the unused Cacophony) makes sound-based attacks useless.
The ability Keen Eye, which acts as an immunity to accuracy reduction.
The ability Scrappy, which lets Normal and Fighting-type moves pummel the Ghost-types that they are usually unable to hurt. The moves Foresight and Odor Sleuth are this in move form. Miracle Eye is an equivalent that removes Dark-types' immunity to Psychic.
Wonder Guard takes this up a notch. Unless the attack that would deal damage is super effective, it does no damage at all. Unsurprisingly, this ability is often found illegitimately in online battles. On top of that, the Pokémon Spiritomb and Sableye have the type Ghost/Dark, which gave them zero weaknesses at all until Fairy was introduced in Generation VI. This means that, if you hacked Wonder Guard onto Spiritomb or Sableye, they would be immune to all normal damage — only passive damage like poison or sandstorms would hurt them. note The one exception is during Generation IV, when Fire Fang always hit due to a glitch.
Tsareena's ability Queenly Majesty and Bruxish's ability Dazzling prevent the opponent from using priority moves.
Mimikyu has the unique ability of Disguise. Unless it's up against something that ignores Abilities, it takes no damage from the first directly damaging attack that hits it. This includes Z-Moves, meaning that you can drop a continent on a Mimikyu and all you'll do is make its fake head fall over. Similar is Eiscue’s Ice Face, but applied only to Physical attacks.
Dewpider and Araquanid's ability Water Bubble both weakens damage taken from Fire-type moves and makes them immune to being burned.
Galarian Ponyta and Rapidash's ability Pastel Veil grants their team immunity to poison.
Arrokuda and Barraskewda's ability Propeller Tail and Duraludon's ability Stalwart let them ignore the effects of moves and abilities that ordinarily cause the user to draw in attacks, such as Follow Me and Lightning Rod.
Urshifu's ability Unseen Fist lets it bypass the effects of protection moves.
The Decidueye family-exclusive ability Long Reach lets them no-sell effects of items, abilities, and moves activated by contact.
Infiltrator lets Pokémon ignore barriers note Reflect, Light Screen, Safeguard, Mist, Aurora Veil and Substitutes.
Moves:
Gastro Acid functions similar to Mold Breaker above, but with all abilities.
Haze functions similar to Unaware.
Clever application of the moves Mimic, Role Play, Camouflage, Skill Swap, Worry Seed, Conversion, and Conversion 2 also could result in this (depending on what move/ability/type is imitated/replaced).
The Diglett and Sandygast lines as well as Mega Gengar bear a unique immunity to Telekinesisnote which works Flavor Text-wise by lifting the Pokémon in the air, by virtue of being embedded in the ground.
Psychic Terrain protects Pokémon that are on the ground (i.e. not currently affected by Levitate, Telekinesis, Magnet Rise, or the passive effect of the Flying type, or had the effect of one of those negated by Smack Down or Thousand Arrows) from priority moves.
Electric Terrain protects Pokémon on the ground from sleep.
Misty Terrain protects Pokémon from sleep, poison, paralysis, freeze, and burn.
Sunsteel Strike, Moongeist Beam and Photon Geyser, the signature moves of Solgaleo, Lunala and Necrozma respectively, have a built-in Mold Breaker effect.
Ground-type Pokémon are immune to Electric-type attacks.
Steel-type Pokémon are immune to Poison-type attacks.
Fairy-type Pokémon are immune to Dragon-type attacks. This immunity is particularly baffling. Don't try to comprehend how something like Jigglypuff is now capable of being clawed, sucked into twisters, having meteors dropped on it, or even being subjected to the time-space warping powers of the god-like Palkia and Dialga without suffering so much as a scratch.
Flying type Pokemon are immune to Ground type moves. This makes sense in a way. However, there are a few moves that are labeled as a Ground type that seemingly aren't ground types, most notably ones with "Bone" in it such as Bonemerang. How throwing a Bonemerang against a Flying type doesn't hurt it at all is baffling.
Dark-types are immune to Psychic-type attacks. As of Gen VII, they are also passively immune to moves boosted by the Prankster ability, which allows the holder to move first if using a status move.
Normal-type Pokemon are immune to Ghost-type attacks (damaging ones anyway, moves like Confuse Ray still work against Normal-types) and vice versa. Ghost types are also immune to Fighting-type attacks (but unlike Normal, Ghost still does damage to Fighting).
Because of how type effectiveness is calculated, type immunities override all other type-vs-type relationships. For example, Electric-type attacks are normally super-effective against Water-type Pokémon, but completely helpless against dual-Water/Ground.
A Pokémon being a specific type will allow it to no sell statuses. Poison and Steel note Due to an oversight in the 2nd gen, Steel types could be poisoned through Twineedle, since it was an attack that could inflict poison but it wasn't a Poison-type attack types are immune to the poison status; Fire types are immune to the burn status; Ice types are immune to being frozen; Grass types cannot be hit by Leech Seed, powder, or spore moves; and starting with X and Y, Electric types can't be paralyzed. Also as of X and Y, Ghost types are immune to trapping moves, Shadow Tag, and Arena Trap.
Non-airborne Poison types will wipe out any layers of Toxic Spikes on their end of the field when sent out.
In Pokémon Red and Blue, Legendary Pokémon often simply evade Poké Balls. This is because they have very low catch rates, and in the first games only, failing to catch a Pokémon on a very low chance of doing so will cause the ball to miss entirely.
Dynamax and Gigantamax grant Pokémon a whole host of immunities for the three turns it's active:
Moves which force the Pokémon out will fail against it.
If a Dynamaxed/G-Maxed Pokémon is holding a Choice item (one that locks it into using a certain move in exchange for boosted attack, special attack, or speed), it won't be active.
Weight-based moves fail against Dynamaxed/G-Maxed Pokémon due to their sheer size.
