The SIG-Sauer P226 is the main pistol of the American troops in the movie. Captain Bergen (Coolio) also uses one as his main sidearm. While it's not entirely correct that all the troops would carry the P226, it is somewhat accurate, since the P226 is used by many different factions of the U.S. Army, and P226s from the 80s (like those in the film) are still being used today.
A CZ-75 is seen in use by terrorists and some American troops, although American troops have never carried CZ guns. In an apparent continuity error, Capt. Bergen's P226 changes to a CZ-75.
M1911A1
An M1911A1 is seen, mostly in the hands of Kate Heinlein (Amy Sloan).
Spanish Replica M1911A1
When Kate Heinlein (Amy Sloan) drops her M1911A1, it turns into an obvious Spanish "Denix" replica pistol.
Rifles
Marlin Camp Carbine-9
Several hunters are caught out in the open when the Pterodactyls attack. One of them carries a Marlin Camp Carbine-9.
AK-47
Classic Milled receiver AK-47 rifles are seen used by terrorists.
AKM
The updated version of the AK-47, the AKM, is seen used by terrorists.
AKMS
An AKMS with a folding stock is seen used by terrorists.
Czech SA vz-58V
The VZ-58V assault rifle with a folding stock is seen used by some terrorists. Though it looks similar to the AK-47, it is a completely different weapon. Like in Lord of War, the VZ-58 may have been used as a cheaper stand-in for the AK-47.
Submachine Guns
Czech Sa.24 Submachine Gun
Also used by American troops is a Czech Sa.24 Submachine Gun mocked up in a modified Muzzelite MZ14 shell, no doubt to mimic similar looking weapons, like the FAMAS. Some are seen equipped with suppressors.
Shotguns
Unknown Shotgun
A shotgun is briefly seen, but never clearly enough to identify.
Prop Guns
Rubber Muzzelite MZ14 shell prop gun
Fake Stunt AK-47
Mocked up M16 Carbine
Fake M203
Mocked up Rocket Launcher aka "The Aduwan"
Other
AK Blank fire adapter
Visible in one scene is a very clear shot of an AK with the Blank Firing adapter seen behind the slant compensator.
Wacky Army Helmets
As is obvious to all viewers, the so called 'U.S. Special Forces' Helmets are plastic Airsoft Kevlar helmets from Hong Kong, but they are covered with the woodland helmet cover for an M1 Steel pot, so they don't fit the airsoft helmets. In one instance, they didn't even bother to give a soldier a helmet, instead, wrapped a woodland camo helmet cover on a 'fishing hat' and taping it down.