Sumotori Dreams is a necessary download, for everyone. It's free, it's under 100 kb, and it's fun, albeit in a horrendously flawed sort of way.

The game is basically a sumo wrestling simulator with a strong emphasis on physics. If you remember the Euphoria physics system that LucasArts is implementing for future Star Wars and Indiana Jones games, this game basically uses a variation of that engine -- essentially, both bots in the game have intelligent, physics-specific AI. If off-balance (which they almost constantly are), their internal physics AI will attempt to right itself. Translation? After one or two shoves, you'll end up with some fluid and quasi-realistic sumo matches, followed by the hilarious slapstick attempts of said robots to get back on their feet.

Basically, take the Rock 'Em Sock 'Em robots, add three bottles of Spanish Fly, and mix thoroughly. Voila: you've got Sumotori Dreams.

As an actual game, it's more or less useless: 90% of your character's motions are based off its internal physical AI, not so much your actual button presses. Still, though, it makes for one hell of a fun tech demo. You may be surprised to find yourself spending more than a few hours finding different ways to make the robots fall on their metallic asses (especially if you find the hidden "punishment" mode).