Generation Iv
Rivalry
Raises Attack if the foe is of the same gender.
Detailed Effect
This Pokémon inflicts 1.25× as much regular damage against Pokémon of the same gender and 0.75× as much regular damage against Pokémon of the opposite gender. If either Pokémon is genderless, damage is unaffected.
Pokémon With Rivalry
18 canonical Pokémon forms can have this Ability.

Nidoran F
Nidorina
Nidoqueen 
Nidoran M
Nidorino
Nidoking
Shinx 
Luxio
Luxray
Axew
Fraxure
Haxorus
Litleo
Pyroar Male
Beautifly
Pidove
Tranquill
Unfezant