The Heavy Tank was a World War II American tank project developed to counter new German tanks, such as Tiger I, Tiger II, and the Jagdtiger. It weighted pounds, had a gun and 11 inches of armor on the turret.
Scorpion Self Propelled Anti-Tank Gun. The was turret-less and the only armor was the blast shield. It was air-deployable and used by airborne units in the Vietnam war. It was replaced by the Sheridan, which had a fully protected turret.