The Machine Pistol is a weapon featured in Mercenaries 2: World in Flames.
There are two different variants of the machine pistol featured in Mercenaries 2. The MAC-10 and the Micro Uzi. They are both exactly the same in terms of performance, with the only differences being the look of the two weapons and who uses them. The MAC-10 is only used by the Pirates. This weapon can also be purchased in the Pirate Supply Drop along with the Shotgun and Desert Eagle-skinned Pistol. When the rum-smuggling contract is active, you should be able to find several of these crates near the rum-carrying pickup.
The Micro Uzi is used by the Venezuelan Gangsters in service of Ramon Solano and can acquired during the mission where the mercenary assaults the villa, or by finding a very large group of them at a secluded base full of sports cars and Uzi-toting gangsters when doing a Pirate HVT. It cannot be obtained from supply drops. Pirates rarely carry the Uzi.
In terms of performance, the machine pistol is very useful. One of Mattias' lines when picking up this weapon is, "A little inaccurate, but it shoots so fast." This should give you an idea as to what to expect from this weapon. The machine pistol has a very high rate of fire, and therefore lacks good accuracy. If used in bursts, the machine pistol does not become much more accurate, so it isn't recommended to use this weapon for long range fire fights, and only really excels in close and medium range. The oversized magazine will allow the shooter to fire off an unrealistic amount of bullets before reloading, and has even more in reserve. This gun actually has the lowest damage of all guns, at 10 shots to kill a VZ regular troop. It redeems itself with rate of fire.
A sub-machine gun--though classified by some as a machine pistol--the MAC-10 (Military Armament Corporation Model 10) was originally designed as a compact firearm for use by Special Forces. Most notably used by Special Forces in Vietnam, it was found not to be easy to control and uncomfortable to fire. It has since gained a somewhat undeserved reputation as a criminal weapon.
The baby brother of the legendary Israeli Uzi sub-machine gun, the Micro Uzi is a compact machine pistol designed originally as a Personal Defense Weapon for those requiring a compact and fast-firing weapon, such as armored vehicle crews.