The Trikke
Apparently it came out in 2003, but I didn't hear about it until just the other day. Basically it's a 3-wheel bike that you propel by shifting your body weight left & right, like cross-country skiing. It folds up for storage too. I even saw someone with a folded-up Trikke strapped to his back like a backpack.
Apparently they have a small but faithfully growing fan club, and people who have customized their trikkes to do tricks. I'd like to get a Trikke T-12, but I'm too heavy for it's 250 lb weight limit.
Trikke Action Videos: on trikke.com TrikkeTalk fan club Parody demonstration of the Trikke 8