Chlorophyll

Chlorophyll doubles the ability-bearer's Speed during bright sunshine.

Game descriptions

Ruby, Sapphire, FireRed, LeafGreen, Emerald:Raises SPEED in sunshine.
Diamond, Pearl, Platinum, HeartGold, SoulSilver:Boosts the Pokémon’s Speed in sunshine.
Black, White, Black 2, White 2:Boosts the Pokémon’s Speed in sunshine.
X, Y, O.Ruby, A.Sapphire:Boosts the Pokémon’s Speed stat in sunshine.
Sun, Moon:Boosts the Pokémon’s Speed stat in sunshine.
Ultra Sun, Ultra Moon:Boosts the Pokémon’s Speed stat in harsh sunlight.
Sword, Shield, B.Diamond, S.Pearl:Boosts the Pokémon’s Speed stat in harsh sunlight.
Scarlet, Violet:Boosts the Pokémon’s Speed stat in harsh sunlight.