Generation Iii
Plus
Powers up with MINUS.
Detailed Effect
This Pokémon has 1.5× its Special Attack if any friendly Pokémon has Plus or Minus. This bonus does not count as a stat modifier. If either ability is disabled by Gastro Acid, both lose their effect.
Pokémon With Plus
10 canonical Pokémon forms can have this Ability.

Plusle 
Klink
Klang
Klinklang
Toxtricity Amped
Toxtricity Amped Gmax
Mareep
Flaaffy
Ampharos
Dedenne