Jason's Robot Ball
I was recently told that there have been some attempts to make a ball which can move itself around by deforming it's own shape.
Here's my latest design for how to make this practical... ish.
There's a motor to turn the blue wheels, and one to move the pendulum with the battery on it. The pengulum swings perpendicular to the image. Having the weight of the pendulum off to one side should be enough to make the wheels turn to that side, at least when they're turning.