May be limited on how much acid that can be produce.
May be limited on what kinds of acids user can produce.
Takes time to control due to the risk of the ability could accidentally destroy items the users didn't mean to destroy.
Magellan (One Piece); technically a poison-user, but one of his poisons behaves more like acid.
Terumī Mei/Fifth Mizukage (Naruto); can produce a kind of vapor that is corrosive
Lily (Code: Breaker)
Gluttony, acidic saliva (FullMetal Alchemist)
Preta Ghoul (Black Cat)
Anarchist (Marvel); could sweat acid and fire acid blasts from his hands.
Man-Thing (Marvel); uncertain whether the acidic burn caused by his powers is mystical or biochemical. Stated in some comics to be "sulfuric acid" though it has been shown to burn even those with superhuman durability.
David North/Agent Zero (Marvel)
Artilas (Geneforge series)
Roamers (Geneforge Series)
The Freaks (Crackdown 2)
Spitter (Left 4 Dead 2)
Marlboro (Final Fantasy); debatable, but Marlboros produce various types of ill effects, one of which could be considered a corrosive acid.
Reptile (Mortal Kombat)
Hazmat (Marvel Nemesis: Rise of the Imperfects)
Viron.Volkov (Storm of the Imperial Sanctum)
Subterran.Unix (Storm of the Imperial Sanctum)
Joseph Bertrand III (Infamous 2)
The Xenomorphs (Aliens); some variants can spit acidic saliva, while all variants blood highly acidic blood.