MP5

The MP5 was a submachine gun developed by Heckler & Koch in 1966. It is still used, and was the basis of the MP5A2 and the MP5SD2.

During Operation 747, Lt. Solid Snake, while investigating the warehouse for any sign of Metal Gear's development by fortress fanatic, he uncovered an MP5, and proceeded to procure it and make use of it.

Behind the scenes
The MP5 appeared in the non-canon NES sequel to Metal Gear, Snake's Revenge, although it was only identified in the instruction manual.

Although the MP5 itself does not reappear in canonical entries to the series, the MP5SD2 appeared in Metal Gear Solid as an exclusive weapon for Very Easy mode, one of the weaker guns in Metal Gear Solid 4: Guns of the Patriots, and as a developable weapon in Metal Gear Solid: Peace Walker alongside the MP5A2.