Robert Neville (Will Smith) uses a semi-automatic Colt AR-15 model that loosely resembles an M4A1 carbine; this variant is referred to in the company's catalog as the "Law Enforcement Carbine" (see http://www.colt.com/law/lecarbine.asp for more info on this model). The LE Carbine is a semi-automatic-only variant 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) scope throughout the movie. The weaponlight on the gun is a PentagonLight MD3R.
Neville's (Will Smith's) sidearm throughout the movie is a Heckler & Koch Mark 23 with a flat earth (tan) frame. He uses the weapon most notably to kill the infected dogs in the middle of the film.
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.
Anna (Alice Braga) draws a Glock 19 on Robert Neville (Will Smith) during breakfast in Neville's home. As the Glock 19 is an issue NYPD weapon, this gun was, again, likely taken from an NYPD precinct.
One of the guards that greets Anna (Alice Braga) and Ethan (Charlie Tahan) is armed with an M16A2. When Neville opens the weapons cabinet there is an M16.
Heckler & Koch SW SP-10s are used by the 2 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."
Used by US Army Personel at the harbor during the evacuation scene. One of the M4A1s clearly has a reflex scope on top, with a regular handguard. Others have regular ironsights. (at the part where Dr. Neville says, "Scan her again!")
