I stand corrected. This is the weirdest story of the weekend!
If you read Joseph Leray's "Nordic New Wave" feature from the other week, you ought to be familiar with Johann Sebastian Joust, a game using accelerometer-powered controllers and no video screen whatsoever. Swordfight, by developers Kurt Bieg and Ramsey Nasser, taps that same social aspect by requiring a pair of modified Atari 2600 controllers and nothing else.
Here's what you do: strap the controllers around your waist, tie your hands behind your back, then use the protruding joysticks to try to press the other person's button. In other words, it's a game about touching heads. Yes, those heads.
Still can't wrap your mind around the concept? There's video.