Scorpion:

Learn about the Scorpion submachine gun in Metal Gear Solid: Portable Ops, its origins, and how to obtain it.

The Scorpion is a small submachine gun designed and produced in Czechoslovakia. It is extremely compact and easy to handle. It uses light .32ACP ammunition, which results in an excellent sense of control even in full-auto mode, despite its small size. The Scorpion was designed for use by special forces and police in Warsaw Pact countries, but it has also been adopted by many international terrorists, giving it a high profile among Western countries.

Obtained: You can find the Scorpion via the Supply Depot Report. Soldiers also carry this weapon.