Unicycle

One wheel motorcycle, invented by Italian M. Goventosa de Udine, 1931

Mr. M. Goventosa of Udine, Italy, built this monowheel in 1931, and that it was capable of 150 KPH, or about 93 MPH. - Hemmings

 I've seen other old monocycles, but the rider was centered sideways within the wheel. This version would give you unobstructed vision directly forward, but with both versions your forward vision would be obstructed. Whether it was better to have the obstruction directly ahead or a few degrees to one side is debatable.

I suspect the big problem with these things is that you could not brake very strongly. Too much force on the brake would send you on a loop-de-loop, which would reduce your braking ability, not to mention dumping you on your head. A cute idea, but not really practical.

There is a modern, computerized version running around where the rider rides on top of the wheel, but once again, I suspect braking is compromised. Whenever you touch the brakes, the wheel needs to speed up just a fraction to get in front of you so that when the brake is applied, 'down' points through the tire's contact patch.

Via daily timewaster, who has a different colorized image of an earler version.