I think they also mentioned when reviewing one of those crazy open-wheelers that it was supposed to be able to drive upside-down simply due to downforce, but I don't think they demo'd that.
F1 teams also commonly claim their cars could drive upsidedown, but the logistics of actually trying that would be absurd. You'd probably need a robotic driver at least...
http://www.youtube.com/watch?v=-TbpgZ2Dt0A
I think they also mentioned when reviewing one of those crazy open-wheelers that it was supposed to be able to drive upside-down simply due to downforce, but I don't think they demo'd that.