M-4A4 Pistol (or M4A4) is a semi-automatic pistol primarily used by United States Colonial Marine Corps, the armed forces of Weyland-Yutani Corporation as well as mercenary units such as Iron Bears in the 2230s.
M4A4 was devised as an update to M4A3 Service Pistol giving the Marines the choice between using the regular anti-personnel rounds or anti-piercing ammunition.
- Anti-personnel rounds: A high-velocity fragmentary projectile that splits up on impact into small shards that can cause damage similar to that of a small explosion to soft targets. 
- Armor-piercing rounds: The round is composed of several layers of material: a non-ferrous outer layer encasing lead shield layer encasing the projectile core itself. The core is made of tungsten alloy. When the projectile strikes the target, the outer layers peel away leaving the point-shaped core to penetrate the target.  The projectiles are powerful enough to penetrate the mesoskeleton of Praetorians.
Many members of the unit of United States Colonial Marine Corps that was sent to investigate the situation on LV-1201 were equipped with this weapon. Most marines use the pistol as a sidearm with the exception of Major Thomas McCain, who used the weapon as his primary during the initial stages of the mission, later switching to M41A Pulse Rifle.
Weyland-Yutani Corporation guards stationed on the planet used the pistol in large numbers as their primary weapon and often complemented it with shotguns and pulse rifles. Iron Bears mercenaries were known to use the weapon and some of its members, such as Major Dunya were known to dual-wield the pistol to a great destructive effect.
- It seems that the design of the pistol was based off the Heckler & Koch Mk 23 Mod 0 bearing only a few differences.
- The pistol is the player's character starting weapon in Aliens versus Predator 2.
- The ability to dual-wield the pistol was added in the Aliens versus Predator 2: Primal Hunt expansion pack.
- ↑ 1.0 1.1 Monolith Productions. Aliens versus Predator 2: The Game Manual, p. 27 (2001), Sierra Entertainment.