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, usually only releasing rare or Legendary Pokémon; occasionally, however, a Master Ball may also release Goldeen.

Master Balls are set to reappear in Super Smash Bros. Ultimate.

Trivia

 * Zoroark is the only non-Legendary Pokémon that isn't Goldeen that can be released from a Master Ball.