The Heckler & Koch G36 visually modified is the futuristic rifle carried by Sarge (Dwayne Johnson), Reaper (Karl Urban), Portman (Richard Brake) , and Duke (Razaaq Adoti). The stocks used are most likely derived from the G36KV stock. According to the ammo counters, the beefed-up box magazines are supposed to hold 65 rounds.
Some of the marine's including Mac (Yao Chin) and Reaper (Karl Urban) use H&K USP handguns as their sidearms. It is most notably seen when Mac hands one to Pinky (Dexter Fletcher) for protection.
IMI Desert Eagle Mark XIX
Sarge's (Dwayne Johnson) sidearm is an IMI Desert Eagle Mark XIX. He most notably uses it to kill a mutated Dr. Carmack. His gun is quite clearly the .44 Magnum version, as evidenced by the fluted barrel in the screenshot below.
Beretta 92FS
Duke (Razaaq Adoti) carries a Beretta 92FS as his standard handgun and is seen using it when running away from the mutated Dr. Carmack.
The Bio Force Gun, adapted from the game's BFG 9000, also makes an appearance in the movie. Like the game, it's the most destructive weapon used. It is wielded by Sarge (Dwayne Johnson). There were two working (vibrating) props of The Bio Force Gun, built from scratch out of resin and fiberglass.
Armory
Several highly modified real-life weapons can be seen in the armory.
Mac's Grenade Launcher
Mac apparently uses a grenade launcher as his weapon of choice, it appears to be an entirely fictional prop as the weapon is never fired in the movie.
SA Vz. 58
During pre-production training, the actors were taught firearms handling maintenance and one of the training guns used was a SA Vz.58 assault rifle. One can see these weapons by watching the bonus content of the Doom DVD.
Norinco Type 85
The Kid (Al Weaver) used a Norinco Type 85 as his training gun. It's seen in the instructional drills if you watch the making of doom documentary.