Machine gun

The MG-88 Enforcer is a weapon in Doom 3. Its default key is 4. The Machine Gun uses ammo from Machine Gun clips. It has very fast rate of fire, but less power than the Pistol. It should be used to mow down hordes of lesser demons or zombies. It can also be used for long-range work against enemies who are hiding behind cover. Take note that the ammo counter is on the weapon itself and not on the HUD.

Tactical Use
Machine guns are good in medium to short range situations against lightly armored foes. Zombies make the best targets being slow and weak.

Machine guns are most effective against Z-Sec's (aside from the ones with Riot Shields) as they take down the lightly armored foes quicker than the pistol due to it's high rate of fire and is more accurate than the shotgun at medium-to-long range. In a tight spot, machine guns are good versus Maggots and Imps as well. On lower difficulties, a player with a good aim can easily deal with a Demon.

The weapons rate of fire has two drawbacks. The first is that rapid fire causes the weapon's recoil to disrupt the players aim. The second is that the weapon burns through it's clip quickly. When using the machine gun, it's recommended that you are near cover in case you need to reload during the middle of a firefight.

This weapon can be first picked up in the Underground. When your in the security center, continue to access the console to open not only the weapon lockers next to the elevator, but also a supply closet that houses a health center, and a plasma cell. Not bad for the second level.

Doom
A machine gun was originally going to be used in Doom, and the marine is shown to have one on the box art and his sprite.