The Liberator was a pistol developed during WW2 that was designed to be dropped from an aircraft into areas occupied by Nazi Germany. The pistol would then be picked up and used by resistance forces or an occupied civillian. It fired the .45 ACP round.
It's intended use was to allow individuals to gain access to a better weapon by killing a guard or lone enemy soldier.
There are few documented instances of the weapon being used as intended and most of the FP45's were destroyed after the war.