The Thing is a 1982 horror film directed by John Carpenter and reunites him with his Escape from New York star Kurt Russell. The film is a remake of the 1951 classic The Thing from Another World and a prequel to this film was released in 2011.
The following firearms can be seen in the film The Thing:
A Heckler & Koch HK93 semi-auto rifle with a scope and a 40 round magazine is used by the Norwegian with Rifle (Kurt Russell's brother-in-law at the time of filming Larry Franco) to try and kill the infected dog while flying from the helicopter. When the helicopter lands the passenger (named Jan Bolen in a deleted scene) emerges with the rifle and continues after the dog while the pilot has a mishap with a grenade. This scene has in part been reproduced for the prequel, and the passenger renamed Lars. Interestingly, any viewers who speak Norwegian would have much of the plot of the movie ruined in this very first scene, as the armed man explains the nature of the threat.
Ithaca 37 shotgun
MacReady (Kurt Russell) carries a Ithaca 37 shotgun several times in the film. At one point Windows (Thomas G. Waites) manages to grab one before he is subdued by the others.
Garry (Donald Moffat) carries a Colt Trooper MkIII in a holster on his duty belt. Midway through the film MacReady (Kurt Russell) gets possession of Garry's revolver and carries it with him from then on.
M2A1-7 Flamethrower
This flamethrower is used by several members of the team throughout the movie. Palmer uses a different flamethrower, apparently a propane powered model sold commercially, used for burning weeds, and removing ice from planes and other equipment; the flame on the propane model is very short, at most usually 7 feet. Even so, many scenes in the film use genuine, military-spec liquid-fuelled flamethrowers, something of a rarity in movies.
MacReady (Kurt Russell) and some other survivors are seen using dynamite bundles to combat the alien. Most notably when MacReady grabs a bundle so nobody will attack or burn him. The survivors fashion the dynamite to their chests with a improvised holder. (In the second photo under Molotov cocktail below, you can see the survivors are using WW2 Thompson magazine pouches to hold the dynamite)