Nimbus Impossible Wheel / BC Wheel Price: $149.00 Want to ditch the frame and just glide downhill? Here is the solution, the Impossible Wheel (also known as the BC Wheel). Just stand on the footplates as the wheel rolls along. The footplates hang below the axle to make this easier.
I've had one of those now for almost 3 years. They are about 10x harder to ride than a unicycle, but fun when you get a long run on it! The novelty kinda wear off pretty quick though.
You can ride one on flat, but the ride will be shorter than if you are going downhill. There are no brakes other than jumping off! Here's an awesome BC video by one of the best BC riders. Very, VERY few can achieve this level of skill on one: [ame=http://vimeo.com/7390720]bc wheel is not dead on Vimeo[/ame]
They Float! Man that's great. What else you got? Somebody was talking about a pogo uni, ever seen one of those?