The following weapons appear in the film Avatar:
The AVR-30 Machine Gun is used as a door gun on the SA-2 Samson tiltrotors, and as an assault rifle by the ten-foot-tall Avatars. The weapon was built around an M60 machine gun, sheathed within CNC machined alloy housings (as well as assorted add-ons), and the end product still bears a close resemblance to the M60. It uses a side-mounted detachable drum magazine (very closely resembling an conical MG42 or MG3 magazine) instead of an ammo belt. The AVR-M60 has a very notable triangular barrel shroud as a subtle nod to the original M60 (which is easily recognisable by its slotted barrel shroud and bipod). Jake Sully (Sam Worthington) uses this during the Thanator attack and during the final battle until he pulls out his grenades. Norm Spellman (Joel David Moore) uses one during the final battle as well.
SN-9 WASP (Custom Break-open Revolver)
A WASP revolver is the sidearm of Col. Quaritch (Stephen Lang) and uses 9mm hypervelocity sabot rounds. He keeps the handgun in a crossdraw thigh holster and is seen using it when he tries to stop the fleeing Samson helicopter, and during the final battle to try to dislodge Jake. (The name for the handgun is taken from the "Avatar Survival Guide".) The handgun is said to be resemble the Russian revolver MP-412. The original prop was actually assembled around a Ruger GP100 .357 Magnum using CNC machined alloy housings over top of the real weapon. Hammer tang was cut off meaning it could only be fired double action and the prop was designed to appear as though it has a break-open action, however it retains the "flip-out" cylinder of the donor weapon (at some considerable technical effort) in order for it to be able to be loaded and fired (blanks). There was only ONE hero prop, and at least one stunt prop (distinguishable by the back of the trigger being filled in as in pic below).
GS-221 Base Carbine unit (Standard Issue Rifle)
The RDA SecFor on Pandora use the fictional GS-221 BCU modular rifle. According to the "Human Hardware" featurette, the weapons are made by the fictional company "MATANZA ARMS CORP.". The props, realized by Weta Workshop, have been built in at least 2 primary variants: the Standard Issue Rifle GS-221 and the Personal Defence Weapon (PDW) variant with a shorter barrel. Col. Quaritch (Stephen Lang) fires a PDW variant at the film's heroes as they escape the main RDA base in a Samson helicopter, before switching to his revolver. From a closer inspection of the weapons, resemblances can be clearly seen to the MR-C (Modular Rifle Caseless) that appeared in Tom Clancy's Ghost Recon Advanced Warfighter series of games.
The full-size version of the GS-221 can also be fitted with an underslung shotgun/grenade launcher, although these are never seen being fired in the film. However, the launcher appears to be a drastically shortened version of the combat shotgun also carried by RDA troops (fitting with the modular theme of the RDA's armaments). The active firing versions of the Standard Issue Rifle and Personal Defence Weapon contained a customized Ruger Mini-14 receiver and shortened barrel. Neither of these blank firing weapons were present with the Australian filming unit due to weapon laws. They were only used by American units.
Seen used by RDA operatives in the trailers. Trudy Chacon (Michelle Rodriguez) and Norm Spellman are seen armed with one in the film.
A semi automatic handgun made by RDA is seen used by a RDA operative before he is pulled off the gunship. A major handguard has been added to the actual weapon. Trudy Chacon (Michelle Rodriguez) holds the handgun on the brig guard while helping to break Jake (Sam Worthington), Norm (Joel David Moore) and Grace (Sigourney Weaver) out of the brig. Jake then handles the handgun as Trudy goes to start up the Samson.
MBS-9M .50 Caliber "Hydra" (Tri-Barreled Machine Gun)
The MBS-9M "Hydra" is a Tri-Barreled Machine Gun that fires .50 Caliber Uranium "Needle" Rounds. Resembling the General Dynamics GAU-19/A, the three barrels on the Hydra do not spin like a GAU, but all three barrels fire in full-automatic simultaneously. The Hydra is seen used as door guns on the Aerospatiale SA-2 Samson, and on the Valkyrie that is used as a bomber. Trudy's Samson, had two auto fired during the battle for the Tree of Souls.
Bush Boss FD-11 (Flamethrower Unit)
Prop seen in the "Human Hardware" featurette. In the movie it is used briefly by a RDA operative to burn plant life during the final battle sequence. According to the "Pandorapedia", a similar but bigger weapon would be an optional equipment for the AMP suit; however this system is not visible in the movie.
GAU-90 30mm Autocannon (Fictional Heavy Cannon)
Carried like rifles by the AMP suits. Col. Miles Quartich (Stephen Lang) and Cpl. Lyle Wainfleet (Matt Gerald) use GAU-90's on their suits during the final battle. The GAU-90 uses 30mm rounds and has two huge sling hooks notably. It has an attached bayonet despite clearly being a long-distance weapon.
Gatling-style Guns resembling the M61 Vulcan are seen being fired from Col. Quaritch's Dragon gunship.
The Dragon Assault Ship, in line with modern-day gunships, is equipped with an unguided rocket pods similar to UB-series launchers fitted to a famous Hind helicopter or a AH-1 Cobra.