Robot that balances on a ball

.... and uses it as a wheel (contact with the ground) for maximum mobility.

Researchers at Tohoku Gakuin University in Japan have developed a robot that stays balanced on a ball, even when it’s pushed or heavy loads are placed on top. Dynamically stable robots like this are better than static bots, which use three or more wheels, researchers say. They can have smaller bases, allowing them to navigate tight corners. And their omni-directional abilities allow them to quickly go in any direction without having to turn around.