I find these one of the interesting machines used by the CIS.
The Armored Assault Tank (AAT-1 or AAT) was a medium-sized repulsor tank used mainly by the Trade Federation and the Confederacy of Independent Systems prior to the rise of the Galactic Empire. These vehicles saw service most notably during the Invasion of Naboo and the later Clone Wars. The AAT was formidable; it was augmented with heavy inches-thick frontal armor that allowed it to plough through walls, and had heavy weaponry. It carried a payload of 55 shells. The three standard-issue ammunition types were "bunker-busters", high explosive shells used for destroying enemy structures such as outposts; armor-piercing shells, used for penetrating heavy armor on tanks; and high-energy shells for anti-personnel and anti-vehicle use. As they are fired, these shells are surrounded in high-energy plasma, which improves their penetration and reduces friction, thus increasing speed. Its crew consisted of four battle droids (one commander, one pilot, and two gunners), and could also carry six B1 battle droids on the hand grips on the outside of the tank The commander typically sat inside the turret of the primary blaster cannon, while the gunners and pilot were positioned in the main hull of the tank. The gunners operated both secondary blasters, and the commander controlled the main turret. The OOM series commander was essential to the function of the rest of the crew; if the commander was destroyed, the crew would cease functioning, often causing the tank to drift out of control.