Legion is a 2010 supernatural action film starring Paul Bettany as the archangel Michael, who comes down to earth to fight for humanity's survival. Warning: Possible Spoilers ahead
Michael (Paul Bettany) finds a weapons cache filled with assault rifles including several M16A2 rifles. Most of the weapons in the racks, however, are the inexpensive spring-powered M16A2 toy rifles, as indicated by the screw holes in the receiver and the M4-style step down in the full length A2 heavy barrel.
Michael can also be seen on some occasions using an M16A2 with an M203 grenade launcher, although he more frequently uses an M16A4 in the same configuration.
M16A4
For most of the movie, Michael's (Paul Bettany's) weapon-of-choice is an M16A4 assault rifle fitted with an M203 grenade launcher. Due to a continuity error, his M16A4 occasionally becomes an M16A2 in some takes.
Heckler & Koch G36K airsoft replica
Heckler & Koch G36K assault rifles are also grabbed by Michael from the cache, appearing to be fitted with G36C-style rail tops. They are never used or seen again for the rest of them film. These are clearly the airsoft replica versions of the G36 as you can see the ejection ports are cast in plastic and the rounds in the mag are stacked side by side as opposed to staggered.
Glock 17
The Glock 17 is wielded by several characters and LAPD officers in the film. Nearly all of the Glock 17s in the movie are 2nd Generation models, although a newer 3rd Generation model is briefly visible in the scene where Michael is reloading all of his weaponry after the first assault by the zombies.
Ithaca 37
Bob Hanson (Dennis Quaid) wields an Ithaca 37 with a sawed-off stock when the possessed woman attacks in the diner.
Heckler & Koch MP5K
The Heckler & Koch MP5K is wielded by Michael along with an M16A2 throughout most of the film. Bob Hanson (Dennis Quaid) also uses one in an attempt to stop Gabriel. All of the MP5Ks in the movie have extended barrels, though only a few have the PDW folding stock.