Save the Queen

Save the Queen has been Donald's ultimate weapon throughout the series, with changing way to obtain it with each game. In Kingdom Hearts it is obtained by winning the Hades Cup using only Sora (this mode is unlocked after winning the Hades Cup for the first time). In Kingdom Hearts II, it is obtained via synthesis.

Save the Queen+
In Kingdom Hearts II there's an upgraded version of Save the Queen named Save the Queen+. Like Save the Queen, it is obtained via synthesis, however, it has a different ability.