The Air Hog Zero Gravity R/C isn't zero gravity or radio controlled. But it does stick to walls thanks to the vacuum it creates via a little fan in the roof. The 5" car gets about 10 minutes of play time on a 30 minute charge, and is controlled via infrared controller. It'll set you back about $50, but really, what's the purpose? If you have walls -- guess what -- you've probably got a floor too!
Hit the jump for another picture and a video of the fun to be had.