Press the Spacebar 2000
Okay, I have to post about this game. I was joking about it to a co-worker, who told another co-worker, and then suddenly our whole team was playing it and trying to out-do each other's scores. Check it out.
It is the world's simplest game... and yet... so hard to master. ;) Your maximum possible score does seem to be highly dependent on your keyboard and USB refresh rate however!