Fluffy
Damage from contact moves is halved. Damage from Fire moves is doubled.
In game description
Halves the damage taken from moves that make direct contact, but doubles that of Fire-type moves.
Pokemon with Fluffy
Using Fluffy in Cobblemon
Abilities are passive and always active, so Fluffy costs you nothing to run. If it is marked hidden on a species above, expect it to be harder to obtain: servers differ in whether hidden abilities come from breeding, an Ability Patch, or events.
See the Pokedex for which abilities each species can have, and IVs, EVs and breeding for how to actually pass one down.