The Colt Detective Special snubnose revolver is most commonly seen gun in the film. This revolver is carried by both Officer Bud White (Russell Crowe) and Lt. Ed Exley (Guy Pearce). Det. Richard Stensland (Graham Beckel) also carries one of these, seen only when he hands it over to his superiors.
Colt Police Positive
Exley tells Capt. Smith that the cook grabbed a .38 caliber revolver but was murdered before he could use it. It appears to be a Colt Police Positive as the frame size and grips are too small to be a Colt Official Police. White disarms Leland "Buzz" Meeks (Darrell Sandeen) of this revolver near the start of the film as well.
Smith & Wesson Military & Police
Nite Owl suspect Ty Jones (Kareem Washington) grabs a Smith & Wesson M&P to try and defend himself from Exley and Carlisle during their raid.
Smith & Wesson Model 30
Officer White plants a Smith & Wesson Model 30 in the hand of rapist Sylvester Fitch (Jeff Sanders). It appears to be a pre-WWII model that has tape on the trigger and the grip.
Smith & Wesson Combat Masterpiece
Capt. Dudley Smith (James Cromwell) appears to be using a Smith & Wesson Combat Masterpiece with a 4" barrel during the climactic shootout at the Victory Motel. The story takes place before 1957 when Smith & Wesson began numbering its models.
Pistols
Colt Government
Sgt. Jack Vincennes (Kevin Spacey) carries what appears to be a Colt Government with customized grips as his duty sidearm, carrying it during the "Movie Premiere Pot Bust" and while arresting the Nite Owl suspects.
M1911A1
Roland Navarette (Steven Lambert) is seen using an M1911A1 when Exley and Carlisle bust in their hideout to arrest the Nite Owl suspects after they escaped. White gets one from his car, giving the pistol and an extra magazine to Exley to use during the final gunfight at the Victory Motel.
Almost as commonly seen as the Colt Detective Special, several LAPD officers carry the 12-gauge Ithaca 37. The Nite Owl shooters were said to have used 12-gauge pump shotguns with a five-shell capacity. Breuning (Tomas Arana), Carlisle, Exley, and White are among the officers seen using this shotgun throughout the film. Carlisle and Exley carry these during the Bunker Hill apartment raid, leading to Exley's "Shotgun Ed" moniker. At the Victory Motel shootout finale, Bud White uses the shotgun with great effect.
Winchester Model 1912
Several Winchester Model 1912 shotguns are seen in the back seat of the '49 Mercury when Vincennes, Exley and other officers are searching for the Nite Owl suspects.