1, 2, 3. It's a game that's decided anything from personal pride to who's driving to who's riding up front to who knows what else! Rock, paper, scissors--or RPS--has a home on the web--and a organization, the World RPS Society, for avid fans of the game.
If you're not familiar with the game or it's just been a while for you, the rules of the game are there to get you up to speed as well as some hints on opening moves. The "gambits" section lists many of the combinations of moves that can be made in a "gambit"--which is a series of 3 moves made for stategic reasons.
The online trainer lets you play RPS alone or practice for world championship--yeah, that's right, the world championship! Pete Lovering won last year's title in Toronto, beating 255 competitors.