After using his purposely-stolen car to track the Korean slavers to their hideout, Tom Ludlow (Keanu Reeves) retrieves a Smith & Wesson 4506 and ammunition from his trunk. He then single-handedly storms the house and kills all four slavers with the gun. It would appear throughout the film he used the 4506 while on duty but uses a customized M1911A1 for his off duty activities.
Very notably, when Ludlow breaks into the house he fires two shots on the first man, five on the one on the toilet, and three on the one with the shotgun, ten rounds, eight round magazine capacity, even with one in the tube that's not possible.
Custom M1911A1
While off duty, Ludlow carries a Custom M1911A1 (likely a Series 80) .45 pistol with raised adjustable sights, beaver tail grip safety, a combat hammer, extended ambidextrous slide stop safety, extended slide release, bevelled magazine well, stainless barrel, and long type combat trigger and is seen using it several times in the film.
Smith & Wesson M76
A Smith & Wesson M76 or its copy, the M-K Arms MK 760 is used by Fremont (Cle Shaheed Sloan) to shoot Washington at the convenience store, and later when Tom Ludlow and Diskant confront the killers at their apartment. The ballistics expert tells Ludlow it was loaded with 9mm FMJs or Full Metal Jackets, meaning simple ball ammo.
M3A1 "Grease Gun"
An M3A1 "Grease Gun" is used by Coates (Common) when he and Fremont kill Washington at the convenience store. The ballistics expert tells Ludlow it was loaded with .45 full metal jackets, meaning it was loaded with .45 ACP ball ammo.
Colt Commander
After Ludlow kills all the Korean slavers, he looks in their couch and finds a beautifully gold engraved Colt Commander, which he then plants on the unarmed man he shot on the toilet.
Colt Anaconda
A stainless Colt Anaconda is used by the masked Korean slaver when Ludlow raids their house.
Beretta 92FS
Several officers throughout the film are seen armed with Beretta 92FS pistols. Cpt. James Biggs (Hugh Laurie) is seen with a Beretta holstered when he first meets Ludlow in the hospital.
Beretta 92FS Inox
Washington (Terry Crews) carries a Beretta 92FS Inox as his sidearm. Shortly before the Korean store is raided by the cop killers, Washington draws his Inox on a stunned Tom Ludlow (Keanu Reeves), who, in spite of his original intention of breaking his jaw, had entered the store to warn Washington of the impending robbery.
Kahr M9098 Elite 2003
One of the Korean slavers carries a Kahr M9098 Elite 2003. Only the Elite 2003 has the polished Stainless Frame. The Kahr M9098 Elite 2003 is the smallest of the Kahr 9mm pistols with a 3" barrel. Once Ludlow raids the Koreans house, he takes his Kahr K9, which he had barely drawn before being gunned down, and uses the Korean's hand to fire two shots into the door to look like he shot first.
Glock 17
Detective Diskant (Chris Evans) uses a Glock 17 as his sidearm throughout the film. When Diskant is shot in Freemont and Coate's apartment, Scribble (Cedric the Entertainer) is forced to pick up the Glock but refuses to shoot Ludlow and is gunned down by Freemont.
Browning M2
Ludlow pretends to sell a Browning M2 heavy machine gun to two of the Korean slavers in order to provoke them into stealing his car and the gun, thus allowing him to track them to their final location. When they first see the gun, they complain how they wanted a machine gun they could carry, not a 120lb machine gun to scratch up his car with.
Remington 870
A Remington 870 with a sawed-off barrel is briefly seen used by one of the Korean Slavers when Ludlow raids their hideout. He manages to hit Tom in the vest with it, before he is killed by Ludlow moments later. The magazine cap clearly shows it is not an Ithaca 37 as it was previously stated, but more likely an 870.
Mossberg 590
Coates (Common) uses a Mossberg 590 with six extra shells in a saddle mount holder during his final confrentation with Ludlow.
Benelli M3 Super 90
Several police officers throughout the film are seen armed with Benelli M3 Super 90 shotguns with saddle mount shell holders. Diskant is seen using a Benelli several times in the film as he aids Ludlow during busts.
Rohrbaugh R9
When Ludlow and Diskant chase down Quicks (Noel Gugliemi), Ludlow traps him in roof barbed wire and removes a Rohrbaugh K9 which he had hidden in his waist.
M1 Garand
Officers at Washington's funeral perform the 21 gun salute with M1 Garand rifles.
Romanian AIMS (AKMS)
When Ludlow and Diskant raid Grill's (The Game) house, he reaches for an AKMS which based on the stock configuration and furnature, is a Romanian AIMS.
Ludlow keeps a stainless J-frame Charter Arms Off Duty hammerless snub-nose that he keeps loaded with .38 hollow points. When being attacked by Freemont and Coates in the store, he draws his .38 and fires all five shots, one of which hits Washington in his right shoulder. When being informed by the ballistics expert, he claims the round mushroomed in his left scapula (despite the bullet clearly seen hitting his right shoulder).
Note: Hollow points do Mushroom, Soft points shatter upon intact.
Kimber Custom II
Both Det. Dante Demille (John Corbett) and Det. Cosmo Santos (Amaury Nolasco) carry Kimber Custom II pistols fitted with LED lights. They mess with Ludlow as he crawls away by firing their Kimbers at him, but Ludlow manages to kill and dissarm Demille with a shovel and kills Santos with Demille's Kimber.
Benelli M4 Super 90
A Benelli M4 Super 90 is seen on the wall rack in the police armory when Ludlow and Diskant load up to face Freemont and Coates.
Heckler & Koch MP5SD5
A Heckler & Koch MP5SD5 is seen on the wall rack in the police armorery when Ludlow and Diskant arm up to face Freemont and Coates. In further shots, the integral suppressor is visible.
CAW 40mm Launcher
A Craft Apple Works (CAW) 40mm airsoft launcher is seen on the wall rack in the police armory when Ludlow and Diskant arm up to face Freemont and Coates. While airsoft guns are rarely used in films, a non-focused background shot is usually fair game for them.