The Glock 34 in 9x19mm is Creasy's (Denzel Washington) sidearm in the beginning, carried in a Kydex OWB holster. At one point in the film when Creasy is teaching Pita by her pool, he is seen carrying the pistol in his OWB holster without a shirt covering it like in most other scenes, and on his other side he has a double magazine pouch. It is the weapon with which he attempts suicide and later uses in the kidnapping scene.
It is interesting to note that Creasy's Glock 34 has a 2nd Generation frame (no accessory rail, finger grooves, or thumb rest) during the scene where he attempts suicide, but later in the film, it does have the (correct) 3rd Generation frame, which was the only factory option available from Glock. This is most likely because the slide for the pistol was blank-adapted separately, and the armory had a shortage of 3rd Generation frames at the time. The -34 slide will fit and work fine on a 2nd Gen frame, though this is not factory standard.
Glock 17
Creasy later carries another Glock, the Glock 17. Used when he kidnaps his first revenge victim, and when he assaults the motorcade and kidnaps the police captain. Later given to Mr. Ramos (Marc Anthony) to kill himself with.
Colt Commander
A Colt Commander is seen during the weapons purchase scene, and later used in the assault on Sanchez' home.
Colt Gold Cup National Match
A Colt Mark IV Series 70 Gold Cup National Match is used to kill the first policeman, who claimed himself as part of the Mexico City Police Department criminal secret society named "La Hermandad", after being tortured.
A nickel plated Auto Ordnance M1911A1 is used by Daniel Sanchez' brother Aurelio Sanchez (Gero Camilo) to shoot Creasy in the chest before attempting to escape.
Browning Hi-Power
During Pita's kidnapping, one of the kidnappers uses a Browning Hi-Power. Creasy examines a Browning Hi-Power during the weapons purchase scene, but doesn't purchase it.
Beretta 92FS
The Beretta 92FS is used by two of the kidnappers.
Revolvers
Colt Detective Special
At Pita's swim competition, a nickel plated Colt Detective Special is used to start the race.
At Pita's practice swim meet, a ? is used to start the race.
Shotguns
Zebala Side by Side Sawed-off Shotgun
This Lupara is full sized when he buys it and presumably sawed off afterwards. Creasy uses this short Side by Side shotgun to blow off the hand of Aurelio Sanchez. Also used in the nightclub.
Remington 870
A sawn off Remington 870 is used by Aurelio Sanchez (Gero Camilo) to threaten the reporter Mariana (Rachel Ticotin).
Submachine Guns
M3A1 "Grease Gun"
While never used on screen, Creasy buys an M3A1 "Grease Gun" from the gun dealer. It's seen in his bag. Note the lack of cocking lever and the larger ejection port typical of the M3A1.
Beretta PM12S
At the money drop one of Fuentes' men uses Beretta PM12S to ripoff the kidnappers.
Rifles / Carbines
AR15 Carbine
Used by a thug at the exchange. It is fitted with a laser aiming module and a C-more red dot sight.