A Winchester Model 70 bolt action rifle is held by Jonesy (Damian Lewis) while he is hunting and later by Henry (Thomas Jane)
Note: In the book, Jonesy used a M1 Garand instead of a Winchester.
M16A2
M16A2 rifles seem to be carried by some of the U.S. Army's 'Blue Unit' soldiers.
M4A1
The M4A1 carbine can be briefly seen being carried by some soldiers.
Colt AR-15 A2 Target
Col. Curtis briefly uses a Colt AR-15 A2 Target with a 24" barrel, free-floating aluminum hand guard, Bell & Carlson thumbhole stock, bipod, and night-vision scope. This exact same rifle has appeared in several episodes of The Outer Limits, The X-Files, The Sentinel, and a number of other movies and TV shows filmed in British Columbia.
Ruger M77
Beaver (Jason Lee) can be briefly seen carrying a Ruger M77 rifle when he gets back to the cabin.
Handguns
Smith & Wesson Model 19 Snub
After embarrassing a patient at the beginning of the movie, Henry (Thomas Jane) almost shoots himself with a Snub-nosed Smith & Wesson Model 19 revolver. Instead, he accidentally discharges it into his diploma on the wall.
Beretta 92FS
A Beretta 92FS pistol can be briefly pulled by a truck driver (Ty Olsson) when confronted by Jonesy.
Heckler & Koch USP
Colonel Curtis (Morgan Freeman) carries what appears to be a Heckler & Koch USP in a shoulder holster. In a deleted scene, he is seen pulling it when a soldier attempts to stop him from taking off in a helicopter.
M1911A1
A nickel-plated, ivory-gripped M1911A1 is used by Colonel Curtis (Morgan Freeman) and later by Lieutenant Owen Underhill (Tom Sizemore). Curtis claims it was a gift from John Wayne.
Submachine Guns
Heckler & Koch MP5A3
A Heckler & Koch MP5A3 is used by Lieutenant Underhill (Tom Sizemore) to stop Colonel Curtis and later by Henry to kill a "Shit Weasel".
Heavy Weapons
M134 Minigun
A Minigun is mounted on Colonel Curtis's AH-6 little-bird helicopter.
M230 Chain-Gun
M230 Chain Guns mounted on AH-64 Apache attack helicopters are seen being fired during the Blue Unit's assault on the aliens and their crashed ship.