actulually, me and my friends tried to make a "real world" tron game one time. We taped sidewalk chalk to a stick and taped the stick on our bike so that the chalk would drag against the ground when you went. We got 4 people to try this only to find out that it didn't work as well as we had planned <_<
Anyway, this we be pretty cool, especially if it was more than 2 players and you copuld change the "play field" size or shape to match various things like a parking lot, football field, baseball dimond, etc.