The first and most frequently-seen weapon in the film, the M16A2 rifle appears as the main weapon of U.S. Army soldiers in the film, including Specialist Tommy Yates (Brian Presley).
M16A4 Rifle
Sergeant First Class Duhon can be seen armed with an M16A4 rifle fitted with an EOTech red dot sight.
Colt Model 733/933
As the protagonists' convoy is entering the city, they pass two soldiers searching and questioning an Iraqi woman. The soldiers are armed with short-barreled M16 carbines which may be either the Colt Model 733s or Model 933s depending on whether the carry handles are detachable or not (they aren't shown closely enough to be certain).
Colt Model 727
One of the soldiers, Specialist Jamal Aiken (Curtis James "50 Cent" Jackson III), carries a Colt Model 727 as his main weapon, with a Trijicon RX-09 red dot sight mounted on the carry handle and a Vortex-style muzzle brake. He also appears to have an M203 leaf sight mounted on the handguard, despite not having an M203 on his weapon.
When Private Owens is shot and killed by an Iraqi insurgent, his M4A1/M203 transforms into an obvious rubberColt Model 733 with what seems to be a fake M203 made out of PVC pipe that is tied to the barrel. The rubber weapon is being used because it's getting dropped, but apparently, the movie's armorer didn't have any rubber M4s in inventory.
FN Minimi Paratrooper
In addition to his M16A2, Yates is also seen using an FN Minimi Paratrooper (standing in for the M249 SAW Paratrooper) when riding as a gunner on one of the Humvees in the convoy, with a 200-round woodland camo cloth ammo bag. It is recognizable as a standard Minimi Paratrooper (and not an M249) due to the design of the hand guard and the lack of a heat shield.
Browning M2HB Heavy Machine Gun
In addition to the Paratrooper Minimis mentioned above, some of the Humvees in the convoy are also armed with Browning M2HB heavy machine guns mounted on the roof, though in a rather odd mounting, nearly flush with the top of the vehicle.
M136 AT4
During the ambush on the convoy, one soldier uses an M136 AT4 to take out an insurgent firing on the soldiers from an upper story window, though is shown holding the weapon backwards.
Beretta 92FS
There are several appearances of the Beretta 92FS (standing in for the military-issue M9) in the film, first seen in the hands of Lt. Colonel William "Will" Marsh (Samuel L. Jackson) during the convoy ambush, then in the hands of an enraged and grief-stricken soldier who threatens to shoot Col. Marsh if he doesn't treat his injured friend when the base is under insurgent mortar attack.
FPK/PSL Sniper Rifle
When the ambush on the convoy starts, the first shot is fired by an insurgent using an FPK/PSL sniper rifle, killing an Iraqi Army soldier with a shot to the neck.
RGD-5 Hand Grenade
When clearing a building during the ambush, Yates kills an insurgent who drops a live RGD-5 hand grenade, though Yates and the other soldiers with him manage to get clear before the grenade detonates.
Norinco Type 56
While pursuing insurgents into a graveyard, one of the insurgents manages to sneak up behind Pvt. Owens, shooting him in the back of the neck with a Norinco Type 56 fitted with an AKM-style slant compensator.
Romanian AK Draco Carbine
Most of the insurgents involved in the convoy ambush can be seen armed with Romanian AK Draco Carbines fitted with side-folding wire frame stocks taken from the full-size Romanian AIMS assault rifle. These appear to be some of the same guns seen in Ronin (which had the same armorers as this movie).
Type 69 RPG
During the convoy ambush, one of the insurgents fires a Type 69 RPG at the convoy, destroying one of the trucks in the convoy. The weapon can be identified by having the sights mounted off-center to allow for the carrying handle.
M1 Garand
During Pvt. Owens' funeral, the honor guard can be seen firing a gun salute using M1 Garand rifles.
Colt Match Target
When talking to his boss about having had his civilian job at a local gun store given to someone else while he was in Iraq, Yates picks up and inspects a Colt Match Target rifle. The Match Target is the "post-ban" version of the AR-15 A2 rifle (itself a semi-automatic copy of the M16A2 that Yates used in Iraq), and was sold during the era of the Assault Weapons Ban (1994-2004). It differs from the AR-15 A2 in that it lacks either a bayonet lug or flash hider.
Mossberg 500
While discussing the termination of Yates' job at the gun store, he owner is seen cleaning a Mossberg 500 with wooden furniture.
At one point, out of frustration for not being able to get effective treatment for a back injury he suffered in Iraq coupled with his girlfriend Keisha (Ginger Ewing) breaking up with him, Aiken causes a hostage standoff at the coffee shop Keisha works at, holding her and the other employees hostage while armed with a Smith & Wesson 4506-1.
Heckler & Koch MP5A3
During the hostage standoff, police SWAT officers can be seen armed with Heckler & Koch MP5A3's with Navy trigger groups, M68 Aimpoint red dot scopes, and Surefire dedicated forend weaponlights.
Remington 700PSS Sniper Rifle
During the hostage standoff, a SWAT sniper is seen armed with a Remington 700PSS sniper rifle with a camouflage paint scheme, Harris bipod, and a pouch of some kind on the side of the stock.
Glock 17
Some of the police officers seen in the hostage standoff can be seen using Glock 17 pistols as their sidearms.
Beretta 92FS Inox
At one point in the film, Marsh has a violent outburst after showing up drunk for Thanksgiving dinner, and then goes to his room and retrieves a Beretta 92FS Inox, the stainless, civilian version of the M9 pistol he used in Iraq. He contemplates comitting suicide, but his wife Penelope (Victoria Rowell) finds him and manages to stop him before he can carry out the act, the incident prompting the Marsh family to seek counseling.