Throughout the Kirby games, Kirby must or could use weapons to defeat the games' final bosses.
In Kirby's Adventure, Kirby's Dream Land 2, Kirby Super Star, Kirby's Dream Land 3, and Kirby 64: The Crystal Shards, these weapons were required to defeat them (or at least needed to defeat a certain boss). Unlike a copy ability, final weapons could not be lost if Kirby gets hit or attempts to drop it.
Starting with Kirby & The Amazing Mirror, however, final weapons were not required. Unlike a regular copy ability, lost final weapons bounce around endlessly unless Kirby swallows them. There was even a way to use certain ones regularly.