A German submachine gun, the MP40 saw extensive service in WWII. Automatically firing 9mm ammunition from a 32-round box magazine, the MP40's rate of fire was considered low, but was an easy weapon to handle due to it's low recoil. Primarily used by paratroopers, platoon and squad leaders, and by weapons crews, it has come to be recognized as one of the iconic weapons of the war.
The MP40 was also known by many allied infantrymen as the "Schmeisser," named after German weapons designer Hugo Schmeisser. Schmeisser did not have an active hand in developing the weapon, but did hold several patents integrated into it's design.
In the gaming world, the MP40 can be found in nearly all WWII-themed games, especially those in the FPS and RTS genres.