Place a straight comb on your friend's knuckled fist. In one swift move, snatch the comb off and try to strike their knuckles with the teeth of the comb. If you miss it's their turn. If they flinch and move before you snatch the comb, you get a free strike.

This is video of an early prototype of the virtual version of that game. It is a mashup of a blogger page and thatsmymouse.com app. There is considerable lag so the game play suffers a bit but you get the idea.

Hope to get a flash version of the game out for ColorWars2008.