Many of the soldiers in the film are armed with M1A1 Thompson submachine guns noted by their triangular "bunny ear" sight housing including Pvt. Kelly (Clint Eastwood) and Master Sgt. "Big" Joe (Telly Savalas). These guns were specially requested by Kelly for his special squad to find the gold behind enemy lines, which is why they are not armed mainly with M1 Garand rifles like a normal squad. Throughout the film, the M1A1 Thompsons sometimes switch with older M1 Thompson submachine guns with more complex bolts and cheaper bolted peep sights on the back with no protective housings.
M1 Thompson
The older M1 Thompson submachine guns are seen in the hands of many soldiers, which had more complex bolts and cheaper style peep sights which have no protective housings like the M1A1s. They are mainly seen switching with the M1A1s throughout the film as a continuity error.
M1 Carbine
Pvt. Fisher (Dick Balduzzi) uses an M1 Carbine which he usually keeps fitted with a rifle grenade launcher fixed on the barrel as his main weapon throughout the film.
M1 Garand
Despite the fact that the M1 Garand rifle was the most commonly employed weapon in the U.S. Army during WWII, the rifle is seldom seen and is never used or fired in the film.
FN BAR Type D
The Belgian FN BAR Type D light machine gun takes the place of the American Browning BAR for the film with noticable differences such as a larger wooden forend, a removable barrel, cooling barrel fins, a pistol grip, and a dust cover which were added to the gun by the Belgian army for it to meet their military requirments. It is most notabley seen in the hands of Pvt. Petuko (Perry Lopez).
I'm having a little trouble with the FN BAR users names so I'm leaving them blank. Anyone feel free to help me out here.
Browning M1917 Water-Cooled
Seen pintle-mounted on the U.S. Sherman tanks under Sgt. Oddball's (Donald Sutherland) command are Browning M1917 water-cooled machine guns, which one tank operator is seen firing at German infantry from inside the tank.
Browning M3
The anti-aircraft version of the Browning M2, the M3, is seen mounted on top of the Sherman tanks under Sgt. Oddball's (Donald Sutherland) command, noted by their perforated barrel shrouds. During the assault on the town, Pvt. Kelly (Clint Eastwood) mans the M3 mounted on Oddball's tank and fires it at a Tiger Tank before the Sherman destroys it with a shot to the weak rear end. The guns appear to be fitted with a muzzle blank adapter which dimensions are clearly smaller than a .50 caliber to allow enough pressure to cycle the gun, though the blanks being fired are indeed .50 BMG blanks.
Browning M2 M1919A4
The Browning M2 M1919A4 machine gun is seen as one of the weapons carried by Kelly's squad and when their vehicles are destroyed by friendly plane fire, SSgt. Crapgame (Don Rickles) is ordered by MSgt. Big Joe to lug the .30 cal around, which he hates and throughout the film he tries to pawn the gun off on others to carry. Like the M3, the 1919 guns in the film are fitted with muzzle blank adapters, more notable on the .30 cals because the muzzles would normally recoil on the real gun but the adapters clearly block them from sight.
Browning M2 M1921
Browning M2 M1921 .50 caliber machine guns are seen mounted on U.S. Tanks and personel trucks throughout the film.
Mk 2 Hand Grenade
Mk 2 Hand Grenades are standard issue with the U.S. Army and all the members of Kelly's squad use them, most notabley MSgt. Big Joe a few times in the film.
Radom Model 35
Taking place of the M1911A1 handgun, which was likely still in use during the Vietnam war, is the Polish Radom Model 35 pistol which bears resemblance to the 1911 pistol but is clearly different.
Mosin Nagant M91/30 Sniper
Pvt. Gutowski (Richard Davalos), the squad sniper, is armed with a Mosin Nagant M91/30 sniper rifle outfitted with a 3.5PU scope. It is a major innaccuracy for him to be using the Russian sniper rifle as the U.S. wasn't even on Russian soil. It would be far more accurate if he had been using a Springfield 1903A4 sniper rifle.
Karabiner 98k
The Karabiner 98k was the standard rifle of the German army during WWII but like many old WWII movies, the MP40 is shown as the main weapon of the Germans (see also Where Eagles Fly), which was the exact opposite in real life. In this film, the Kar98k is actually seldom seen.
MP40
Innaccurately shown as the main weapon of the German Army, the MP40 submachine gun is seen in the hands of almost all the German soldiers in the film.
MG42
The MG42 machine gun is seen mounted on personel trucks and pintle mounted on the Tiger Tanks throughout the film.
Flakvierling 38
Four barreled AA/AT (anti-aircraft/anti-tank) Flakvierling 38s are seen used by the Germans when Oddball and his tanks assualt the train station and they are all destroyed before they inflict any damage on the tanks.
Luger P08
Oddball (Donald Sutherland) keeps a Luger P08 pistol as his sidearm of choice, which somehow seems to fit his quirky character. Instead of keeping it in a Luger holster, he keeps it in the poorly fit U.S. 1911 holster.