Metal-Ball powered unicycle
This Metal-Ball powered unicycle harnesses the power of gravity and friction to move it forward and kind of pushes light objects out of it's way. it is also a bit fragile but if you are careful it will stay together perfectly. You should push from the front ''cup'' for better results. I also have a movie on bricksafe to show you powerful it is with the metal ball inside the ''cup''. You can also use a marble if you don't have the metal ball. The size has to be 18-19 mm.