I Am Legend is the 2007 science fiction action film that stars Will Smith as an Army doctor who struggles to find a cure to the virus that has affected nearly the entire population of the world. The film is the third official film adaptation of Richard Matheson's sci-fi novel of the same name, the first being 1964's The Last Man on Earth and the second being 1971's The Omega Man starring Charlton Heston.
The following weapons were used in the film I Am Legend:
Dr. Robert Neville (Will Smith) uses a Heckler & Koch Mark 23 with a flat earth (tan) frame as his main sidearm. He is seen with it holstered, but also carries one in the driver's door, most notably to shooting the infected dogs in the middle of the film. There were several identical firing Mark 23s used on-set, as well as rubber versions for stunt work. For most scenes where Will Smith carried the weapon in the holster, a lightweight airsoft Mark 23 (with frame painted tan to match the firing pistols) was used.
Robert Neville (Will Smith) draws a Smith & Wesson 5946 on Anna (Alice Braga) and Ethan (Charlie Tahan). The 5946 in the DAO setting is one of three pistols used by the NYPD (the other two being the Glock 19 and the P226 DAO), so it was likely recovered by Neville from an NYPD precinct.
Special Weapons SP-10s are used by the two Army Rangers that escort Dr. Neville to the dock. The first seen when Neville says, "Five minutes, we'll make it". The second when Dr. Neville orders the other troops to "get your hands off my wife".
Robert Neville (Will Smith) uses a semi-automatic Colt AR-15 model that closely resembles an M4A1 carbine; this variant is referred to in the company's catalog as the "Law Enforcement Carbine", or the Model 6920 (see http://www.colt.com/law/lecarbine.asp for more info on this model). The LE Carbine is a semi-automatic-only variant of the M4 with a 16" barrel, but according to the Propstore of London, the weapon was modified to fire automatic for the film. His AR is also equipped with an ACOG (TA31 Series) sight attachment throughout the movie. The tactical light on the gun is a Pentagon MD3R.
One of the guards is armed with an M16A2 when Anna (Alice Braga) and Ethan (Charlie Tahan) reach the safe haven. Several US soldiers armed with M16 rifles at the checkpoint seen in a flashback.
The M4A1 is used by US Army Personnel at the harbor during the evacuation scene. One of the M4A1s clearly has a C-More reflex sight on top and a regular handguard. Others have regular iron sights. (at the part where Dr. Neville says, "Scan her again!")
When Neville (Will Smith) opens up his closet arsenal, a long rifle can be seen on the right next next to his M249 SAW. This rifle appears to be a DPMS Panther LRT SASS rifle.
