A little idea I thought up last night.
Basically, you get a group of dedicated wardrivers together and then hide an AP somewhere in the city. This could be a friends house, some office space you have access to, or whatever works.
The group of wardrivers previously mentioned have to find your particular point or series of points to win.
Another variation would be to map a large square of area in a city as the playing field. Then one person with a laptop set to ad-hoc and with filesharing enabled would be the "mouse" . The point of the game would be to "tag" the mouse's wireless laptop by dropping a file on his open share. This game would probably require two man wardriving setups to make it safe.
Me and a few friends played tag the other day and its actually really neat. I used mappoint to plot the points where i picked his wireless up and figured out eventually that he was sticking to a few of the same roads. So I got my driver to wait on the corner or two roads that looked like they were being used and tagged him good when he stopped at the lights.