Like an armadillo or a pill-bug, Cannonbolt is able to curl himself into a ball, keeping his arms, legs and face inside and only revealing his yellow plate armor on his back outside. In this form he is able to quickly roll and bounce around, slamming into his enemies as his main form of offense.
One might wonder how does Cannonbolt know where he's going and not accidentally bump into his allies while in ball form.
Well Duncan Rouleau, who is part of Man of Action, the creators of the original Ben 10 series and currently working on the reboot, answered this question.
Apparently, Cannonbolt has short hairs on his body similar to humans. These hairs are similar to a cat's whiskers and can sense motion and shifts in the air. While not confirmed, it's possible that these hairs are located on Cannonbolt's black lining around his armor, as these lines are exposed outside while he is in ball form. Cannonbolt also has enhanced hearing. With these two senses together, Cannonbolt has something similar to echolation that gives him eyeless vision, allowing Cannonbolt to "see" around him while rolling around in ball form.
