Droideka
Droidekas (also known as Destroyer droids) are a model of tripedal military droid fielded by the Trade Federation and later, the CIS. Of Colicoid manufacture, droidekas provide heavy weapons support for droid infantry.
Features
While droidekas do not walk very fast, they can move quickly by curling up into a ball and rolling, enable them to redeploy rapidly on the battlefied. They are armed with two double-barrelled, automatic blasters, making them powerful anti-infantry units. Some models carry shielding capable of resisting blaster small arms, but such droids can not move while their shields are active.
With their rapid fire and shielding, high-end droidekas could pose a significant threat to Jedi, since the usual Jedi tactic of knock laser fire back with a lightsaber didn't work because the droideka's own fire couldn't pierce its shield. Their high cost, however, limited their production. They saw service during the Battle of Naboo and during the Clone Wars (though they were considerably less effective in the latter because Clonetroopers carried big guns that could easily break through their sheilds), but -- like the rest of the Confederacy's droid armies -- were de-activated at the Clone Wars' end.