Another variation that I have found unique to my college (New College of Florida) called Cowboy, Ninja, Bear:

It is played thus:

The two players start standing back to back. Then they each take three steps (counting out loud, syncronized. Best when someone else counts), turn and "shoot". Cowboy is normally done by pretending to draw two pistols. Ninja is conveyed by a vaugely martial-arts stance. To choose bear most people raise their arms, form their hands into "claw" shapes and make a menacing face. It varys depending on the individual.

Ninja beats Cowboy because he is stealthy and can kill the cowboy in his sleep.

Cowboy kills Bear with his pistol (and the cowboy also represents rapid westward expansion, depriving the bear of its natural habitat).

Bear beats Ninja because it is a fucking bear.

This form of rock, paper, scissors is used to settle minor student government debates.