I saw this on TV a while back and if I'm ever anywhere near the west coast, will have to make a trip to check this out:
6 Flags X Coaster The grainy pix on the website don't do it justice. You sit in a seat that's suspended to the side of the car, nothing around you, and spin around (head over heels) independently of the track direction via a second "track within a track" that controls the spin of the seat axis/spindle. I'm having a hard time describing it in words here, but it looks like the ultimate mindf#ck...
-Peter