Generation Iii
Stench
Helps repel wild POKéMON.
Detailed Effect
This Pokémon's damaging moves have a 10% chance to make the target flinch with each hit if they do not already cause flinching as a secondary effect. This ability does not stack with a held item. Overworld: The wild encounter rate is halved while this Pokémon is first in the party.
Pokémon With Stench
10 canonical Pokémon forms can have this Ability.

Grimer
Muk
Stunky
Skuntank
Trubbish
Garbodor
Garbodor Gmax
Gloom
Koffing
Weezing