The Colt Model 733 carbine appears in the film in the hands of Johnny "Goodboy" Tyler (Barry Pepper) when he's supervising fellow humans at Fort Hood organizing an attack against the Psychlo aliens occupying Earth.
Several M16 rifles can be seen in the film, first seen among the supplies taken from Fort Hood, later in the hands of some of the humans that battle the Psychlos.
Many of the humans involved in the battle against the Psychlos can be seen armed with Colt 9mm SMG's, seemingly having the front sight and muzzle brake removed. Some of them also have lengthened barrels to accomodate the mounting of M203 grenade launchers, as described below.
Some of the humans battling the Psychlos can be seen using M16A1 rifles and Colt 9mm SMG's fitted with M203 grenade launchers during the final battle. The mounting of the M203 on the Colt SMG is rather odd combination, very rarely seen in films.
During the battle against the Psychlos, Carlos (Kim Coates) destroys a Psychlo flying machine using a Carl Gustav recoilless rifle, the weapon incorrectly shown being used as a surface to air homing missile. Carlos later uses one to shatter the massive dome over the city, resulting in the deaths of the Psychlos who are unable to breathe in Earth's atmosphere.
During the battle, Chrissy (Sabine Karsenti) can be seen engaging the Psychlos with an ARWEN 37, the weapon being covered in Hollywood embellishments and depicted as firing high-explosive grenades.
