Dragon Ball - episode 37 - 04 Nov, 1986

Goku enters the fourth floor of Muscle Tower and finds himself in the middle of a forest. Ninja Murasaki who is hiding, has been sent to kill Goku. After games of hide and seek, racing and shuriken throwing, Ninja Murasaki finally decides to fight, and Goku breaks his sword with the power pole. Murasaki throws a boomerang at him which hits and knocks out Goku. (Source: Wikipedia)