Pester Ball
From Bulbapedia, the community-driven Pokémon encyclopedia.
Pester Balls are multi-colored balls that at first appear to be regular Poké Balls. However, instead of catching Pokémon, they release a noxious Pokémon repellant that can knock out or stun Pokémon.
In Pokémon Snap, Prof. Oak gave Pester Balls to Todd to help him flush out wild Pokémon.
Pester Balls have never been used in any other game, though they may be made from the same chemical found in Repels.
