The Shotgun of Doom 3 is a devastating close-range weapon. It can be first found in Mars City Underground on either a shelf or in the large room with multiple generators.
Like the classic version, the Doom 3 Shotgun is the pump-action version, and holds 8 shells at any one time. It is also the only weapon in the arsenal which allows for firing during reloading. Ammunition for the shotgun is in the form of small packets of Shells or large boxes, as well as deceased Shotgun-wielding Z-Secs. The Shotgun also has a "double" shell reload action: although the reload animation shows the player loading only one shell at a time, the loaded ammunition counter increases by two - this is perhaps to save time and provide a faster reaction to the player so they won't be vulnerable to enemy attack during a delayed reload process.
In contrast to the classic shotgun, which allowed players to snipe enemies from several yards, Doom 3's Shotgun is almost useless at long range, as it cannot kill even a healthy zombie over 15-20 feet away. To make up for this, it is twice as powerful as the original shotgun at close range (in effect doubling its function as a replacement for the original Super Shotgun).
Due to the view model being shown as diagonally turned left in the player's hands, the Shotgun in Doom 3 does not feature any open sights like the original shotgun (which was centered in the forward position), so it does offer a guide to aim accurately without the aid of the crosshair presented on the HUD.
As much of the fighting takes place in close quarters, the Shotgun is a dominating weapon for the majority of the game. It works best against Imps, Zombies, and Cacodemons, since they try to rush the player, giving the shotgun's high short range damage an advantage. To maximize ammo efficiency, remember to get very close to your target before firing so that as many pellets as possible make contact with the target. If an enemy has a melee attack, trick it into using the melee attack, then shoot. This works best for Tentacle Commandos.
The Shotgun is useful until the start of Delta Labs, where it would fall as a secondary weapon. Powerful enemies such as Mancubi and Arch-viles start to appear, which will require players to take them down from range. It is strongly recommended to avoid using the Shotgun against such stronger enemies at close range. As they are likely to survive a full shotgun blast a blank range, this will put players at a vulnerable state of taking heavy damage from these enemies' close range counterattacks. However, once you soften them enough from a distance, you can get up close and unleash the Shotgun to finally take them down.
For weaker enemies that usually die from one shotgun shell, if most of the pellets make contact but the target is still alive, the player can quickly draw either the Pistol or Machine Gun and finish it off to maximize ammo utilization.
- The Marine in Doom 3 is often seen wielding the Shotgun in cutscenes of the game. He is also seen wielding it in the official artworks. Due to this, as well as the fact that much of the fighting takes place in tight corridors, the Shotgun is considered to be the flagship weapon of the game.
- The model of Doom 3's Shotgun looks vaguely similar to the Franchi SPAS-12, without the adjustable butt stock. Questionably, the in-game version also has a hook shaped lug attached to the lower barrel (magazine tube), such functionality serves no purpose in real life.