A blitzball is a ball used in the fictional sport of the same name. It is the main pastime of Spira, the world of Final Fantasy X. One of the game's main characters, Wakka, is a blitzball player, and uses the object as a weapon. It is essential for taking down flying enemies since they have more agility and they usually dodge attacks from other characters.
There are many weird weapons in RPGs, but a ball has to be one of the strangest ones. During the game, Wakka acquires multiple versions of the blitzball, with spikes, big spots, etc. It would be cool if other role-playing games had fun sports that served as minigames, and a character that uses an item related to this discipline to attack.