The Thompson, the first gun called a "Submachine gun"
The first original model, the M1921 was supposed to be shipped out in WW1 but production got delayed, it was expensive and heavy.
A newer version was made, the M1, later updated to the M1A1, cheaper to make, lighter, lower rate of fire and in general better.
LShift (Left Shift): Fire
H: Aim (Stabilize, good to negate muzzle rise or for when a person is holding it)
To put in someones hands, disable collision on the arms and put a few phaselinks from the big part in the grip, 2 major stock parts and the biggest part of the top receiver