The Clone Wars
Wheel droideka-1-

A Droideka in wheel form

The Droideka or Destroyer Droid was a battle droid used by the Separatists during the Clone Wars era. These units were powerful battle droids who could combat both Jedi and clones. These droids were capable of collapsing into a ball and rolling at high speed. When in upright position, Droidekas could generate a shield capable of protecting them from conventional blaster weapons while unleashing a devasting barrage of fire from their primary guns mounted on each arm.