The predecessor to Unit 1
The Madox-0 is a prototype built during the Madox design program. Although not as powerful or advanced as the Madox-01 it proves to be quite powerful in the hands of a capable pilot such as Ellie Kusumoto. Unit 0's legs are damaged by the Japanese Defense Force using portable shoulder fired rockets. She gives her auto cannon to Koji to use (as his minigun is out of rounds) to face off with Lt. Killgore.
Its only built-in weapon is a retractable spike in the left arm for hand-to-hand combat.
In the anime Ellie equips Unit 0 with a 35mm Rifle Cannon.