Rai-Dei is a samurai who seeks the knowledge learned only when facing death. He carries a sword with a built in gun that can be fired from the hilt, and is able to swing it with enough force to create a sonic blast. In the anime, he expresses anger in the fact that Vash is refusing to make his mark true and aim to kill, claiming he wants "a real battle".
In the manga, he wears "roller skates" that allow him to move at phenomenal speeds.
(Source: Wikipedia)