M-1 Abrams Air-Ground Defense System (AGDS)

Proposed air defense version of the M-1 Abrams to replace the venerable M42 Duster. Armed with two 35mm Bushmaster cannons and anti-air missiles, it would have used a stock M-1 chassis with a modified turret. The project never went beyond the proposal phase.

via SNAFU and Topwar.ru