M1 Garand rifles are the most common weapons in the hands of U.S. Marines. Most notably seen used by Private Pappas (Mark Ruffalo) and Private Nellie (Martin Henderson).
M1928 Thompson
Sgt. Joe Enders (Nicolas Cage) uses an M1928 Thompson fitted with a 50 round drum during the opening scene in the swamps of Guadalcanal.
M1928A1 Thompson
For the remainder of the film, Sgt. Joe Enders (Nicolas Cage) uses an M1928A1 Thompson fitted with a 30 round magazine (although the capacity is continually ignored, being a John Woo film). Sgt. Pete "Ox" Anderson (Christian Slater) also uses an M1928A1. Since this is a Woo film, whenever Enders or Ox comes running in, all it takes is a good hip fired burst from their Thompsons and all the Japs are dead.
Both Private Ben Yahzee (Adam Beach) and Private Charlie Whitehorse (Roger Willie) use M1 Carbines throughout the film. This is strange because usually M1 Carbines were issued to soldiers of higher rank, not first time translator privates. It would be more likely for them to be issued M1 Garands.
Browning Automatic Rifle M1918A2
Private Chick (Noah Emmerich) uses a Browning Automatic Rifle M1918A2 as his role of the support gunner in the film, although his BAR is firing on the faster auto fire rate and has the bipod removed, suggesting it is used more in the assault rifle role.
M2-2 Flamethrower
Private Harrigan (Brian Van Holt) uses an M2-2 Flamethrower as his weapon in the film. Using a flamethrower in any combat situation is a brave move as a single hit from an FMJ round to the tank containing a mixture of Napalm and Gasoline, and the tank will explode and engulf the user in flames. Harrigan is unlucky enough to experiance this himself, forcing Sgt. Joe Enders (Nicolas Cage) puts him out of his misery with his .45.
Winchester 1897
Gunnery Sergeant Hjelmstad (Peter Stormare) uses a Winchester 1897 "Trench" gun as his weapon in the film, although he is never seen firing it.
Springfield M1903A3
Some of the Marines during the opening scene in Guadalcanal use Springfield M1903A3 rifles. While the M1903A4 was usually issued as a sniper rifle, sometimes '03A3 rifles were used due to M1 Garand shortages.
M1 Bazooka
An M1 Bazooka is used by Marines during the battle of Saipan. When two Marines are attempting to take out a bunker with the device, the loader is wounded and the gunner is killed, so Sgt. Pete "Ox" Anderson (Christian Slater) runs out and does a stylish "judo-roll", grabbing the launcher in the process. The wounded loader gets back up and readies the weapon, and Ox takes out the bunker single handedly. Some other Marines are also seen carrying them.
Browning M1919A4
Browning M1919A4 machine guns are seen both pintle mounted on US jeeps and mounted on M2 tripods in the hands of the infantry.