Splash

Only available to Magikarp, and undoubtedly the worst move in the series of Pokemon games, Splash is a move which does no damage to any foe it is used on.

The move has 40 PP, and a rating of 0 Power.

Rumour
Soon after the release of Pokemon Red/Blue, a rumour sprung up about Splash. According to the rumour, raising a Magikarp to a high level (around Lv60+) would make Splash actually damage a single foe: Kadabra. This rumour was quickly extinguished with the discovery of the Missingo/Rare Candy glitch.