A Heckler & Koch HK416 is used by John Connor (Christian Bale) for much of the film. The HK416 is fitted with a C-More red dot sight, flip up iron sights, and a Surefire Millennium Universal Weaponlight on the right rail. He uses it to shoot a T-600 in the head and to fire at Hydrobots when his chopper crashes in the river.
M4A1 Carbine
One of the refugees that ambushes Kyle Reese (Anton Yelchin), Star (Jadagrace), and Marcus Wright (Sam Worthington) is seen armed with a standard M4A1 Carbine fitted with a Surefire tactical light. Several M4s are also seen loaded in a weapons rack on the tanker truck, also fitted with Surefire tactical lights.
M4A1 Carbine with M203 Grenade Launcher
Several members of the resistance are seen armed with M4A1 Carbines fitted with underslung M203 grenade launchers. Most of them appear to be fitted with C-More red dot sights.
M4A1 Carbine with M26 MASS
John Connor (Christian Bale) uses an M4A1 Carbine with an M26 Modular Accessory Shotgun System attachment, a C-More red dot sight, a Surefire tactical light, and standard iron sights when he goes to the Skynet compound to rescue Kyle Reese (Anton Yelchin). He later detaches the MASS from the M4 and uses it to ineffectively combat the T-800. Due to the lack of a pistol grip on the weapon, he is forced to fire it from an awkward stance to handle the recoil.
A DSA SA58 OSW is carried by Captain Jericho (Terry Crews) at the start of the film. A resistance fighter is also seen carrying one while searching the sewers. The DS Arms SA58 OSW is a short barreled, modern version of the FN FAL .308 battle rifle.
AKMSU
One of the resistance fighters searching the underground manufacturing plant is seen armed with an AKMSU. Later in the film a refugee that ambushes Kyle Reese (Anton Yelchin), Star (Jadagrace), and Marcus Wright (Sam Worthington) is also seen armed with one.
Magpul Masada
Barnes (Common) is seen armed with a Magpul Masada near the end of the film.
FN FS2000
FN FS2000 rifles are used by some of the T-600 robots.
Heckler & Koch UMP-9
One of the members of John Connor's squad at the beginning of the film carries a Heckler & Koch UMP-9. After the raid, when Connor returns to base, one of the resistance members is also seen with a UMP-9, but only the stock is visible.
Full-sized IMI Uzis are seen in the hands of various resistance fighters listening in on Connor's radio message.
Heckler & Koch Mark 23 Mod 0
The Heckler & Koch Mark 23 Mod 0 is carried by John Connor (Christian Bale) as his sidearm throughout the movie. He notably makes a tactical transition from his HK416 to his Markk 23 while engaging HydroBots and then levels it at Marcus Wright (Sam Worthington), who emerged from the same water. A pilot during the river scene also uses one to neutralize a hydrobot.
IMI Desert Eagle Mark XIX
An IMI Desert Eagle Mark XIX with a black finish is used by Blair Williams (Moon Bloodgood) as her sidearm in the film. A crazed survivor (Michael Papajohn) takes it and holds it on her, but she reacquires it from him after informing him the weapon is not chambered and shoots him in the leg. In a scene from the director's cut, General Ashdown (Michael Ironside) is seen drawing a stainless Desert Eagle Mark XIX on John Connor. His Desert Eagle is only briefly seen in the original cut, when he holsters it while onboard the submarine.
Ruger GP100
The Ruger GP100 is seen in the hands of a California refugee when a Harvester Terminator grabs the man with the Heckler & Koch MP5SD6 and pulls him through the roof.
An FN M240B General Purpose Machine Gun is mounted as a turret on top of the cab of the tow truck.
Browning M1919A4
A Browning M1919A4 belt-fed machine gun is mounted on the rear of the tow truck.
Unknown AA guns
Dual mounted AA guns are also mounted on the rear of the tow truck.
M60D
M60Ds are seen as part of an M23 Armament System mounted on the Huey helicopters of the Resistance. Connor uses one from a downed Huey to destroy a damaged T-600 Terminator. John later uses one to fire at Marcus Wright when he escapes from the Resistance Compound.
Dillon Aero M134 Minigun
The Dillon Aero M134 Minigun is the main weapon of the "Infiltrator" rubber skinned T-600 Terminator. This Minigun is held in a single hand by a forward mounted pistol grip supported aft by a gauntlet around the Terminator's forearm. This format makes Brian Steele (the actor who did the motion capture for the T-600) the second actor to fire a Minigun one-handed, the first to fire the full-size version. Actor Matthew G. Taylor was the first when he carried a cut-down version as the Nemesis in Resident Evil: Apocalypse. A Minigun with a GE style barrel clamp and vented flash hider is also seen mounted on the PaveHawk helicopter near the end of the film. The tow truck also has a pair of forward facing Miniguns mounted on either side of the cab.
M203 Grenade Launcher
Along with an Minigun, the T-600 (Brian Steele) has a modified M203 grenade launcher mounted on its left arm. The Terminator fires the M203 randomly at the building Kyle Reese (Anton Yelchin) hides in. In the battle in Skynet's Terminator factory, John Connor also uses an M203 along with an stand alone M26 MASS before giving it to Kyle Reese. Reese also uses an M203 on a moto-terminator. This was most likely taken off the terminator he crushed earlier. The grenade rounds used by Connor looked to possibly be MEI HELLHOUNDs; four are stowed on Connor's left forearm but couldn't be readily identified for certain. The rounds used by the T-600 and the method of reloading were not shown or clearly visible. It should be noted that the T-600's grenade launcher has a flexible hose leading from the rear of the weapon to his ammo pack. It might be intended to be part of a loading mechanism for a multi-shot grenade launcher.
AT4
John Connor is firing an AT4 anti-tank weapon at a disabled Hunter-Killer.
RPG-7
Barnes is seen with the RPG-7 rocket launcher, firing it at Marcus and Blair when they attempt to escape, but miss.
Remington 870
A Remington 870 shotgun fitted with a door breaching break and saddle shell holder is the main weapon of Kyle Reese (Anton Yelchin). He uses it during the chase scene to fire at the Moto-Terminators and uses it to shoot the tanker. He also uses it to threaten Marcus Wright (Sam Worthington) to take off his jacket and to protect Star from the San Francisco scavengers.
M26 MASS (Modular Acessory Shotgun System)
While he first has it mounted on his M4, Connor uses the M26 Modular Accessory Shotgun System by itself when he gets into close quarters combat with a T-800. This is also Connor's weapon in the future war sequence in Terminator 3.
Remington 870 Entry Gun
Used by Barnes (Common) in a promo. He uses this weapon to knock out Marcus Wright.
One of Connor's men at the beginning of the film carries a Benelli M4.
Moto-Terminator
A new menace for the humans, the "Moto-Terminator" (as named by McG in an interview), is a motorcycle-based terminator with auto lowering miniguns on its sides. A pair of Browning M1919s are also visible on the side. It's almost positive that there is another Minigun and another pair of Brownings on the other side. The final film version has plasma cannons replacing the Miniguns, and no Brownings.