Master Ball

The Master Ball is an item from the Pokémon series and is a more powerful version of the Poké Ball. In the games, it is generally given to catch rare and Legendary Pokémon due to its catch rate of 256, allowing it to catch any wild Pokémon it is thrown at. It is introduced as an item in the Super Smash Bros. series in Super Smash Bros. for Nintendo 3DS / Wii U, where it appears as a variant of the normal Poké Ball item, typically releasing rare and Legendary Pokémon.

Trivia

 * Goldeen and Zoroark, despite not being Legendary Pokémon, are one of the Pokémon that can be summoned from a Master Ball.