Chelios gets his hands on a Kahr K9 pistol which he uses to threaten the Warehouse Rooftop Hood (Noel Gugliemi) on the textile mill roof before throwing him off. He then uses it for the start of the shootout in the mill before it runs out of ammo.
SIG-Sauer P226
One of the thugs in the textile mill is armed with a SIG-Sauer P226 and has it taken by Chelios after he jams his hand into a sewing machine. He uses it for the second half of the shootout before trading it with a Glock 17. Also one of Carlito's guards has one tucked away in his pants.
Glock 17
When interrogating Orlando in the club, one of the gangsters draws a Glock 17 2nd Generation and holds it on him. Later in the film, one of the shooters in the textile mill uses a Glock 17 to shoot at Chelios before Chelios kills him and takes the gun for his own use.
Later in the film during the roof shootout, one of Don Kim's thugs uses a Glock 17 fitted with a sound suppressor.
Glock 17 (converted to full auto).
One of Don Kim's thugs is seen using a Glock 17 Converted to full auto. fitted with a 33 round magazine. Although in unfocused background shots the gun is clearly seen firing, in close up shots the gun has the slide locked back and is not firing. Why they chose to do this is unknown.
FN Five-seveN
Chelios is seen using an FN Five-seveN as he prepares to kill Don Kim (Keone Young). His is fitted with a laser and a thread on suppressor.
Beretta 92FS
A Beretta 92FS is seen in the hands of one of the gangster in the club and is the standard issue sidearms of the police department. Chelios steals a Beretta off an officer at one point and taunts his with it before tossing it away to give him enough time to steal his bike.
At one point in the film, an assassin tries to kill Chelios and his girlfriend Eve (Amy Smart) with a sound suppressed Beretta 92FS but Chelios kills him before she is even aware.
ISS Flashpaper Beretta 92FS
Some of the thugs during the rooftop shootout are seen using Beretta 92FS flashpaper guns.
Smith & Wesson Model 500
To stay faithful to the character of a typical villain expression, "A little pussy with a big gun in his hand", Ricky Verona (Jose Pablo Cantillo) wields the most powerful production revolver, a Smith & Wesson Model 500 with a 4" barrel as his sidearm in the film. He is most prominently seen using it during the roof shootout, in which Chelios throws a wine bottle at Verona's hand, causing him to drop his Model 500, which fires and blows off four of his fingers. One of the gangsters in the club is seen with one as well.
When Chelios tries to interrogate Orlando, several of the gangsters in the club draw Desert Eagles. One of these Desert Eagles is an Early Mark I in .357 Magnum, the other is a flashpaper gun. Chelios later acquires one of these Desert Eagles off of Verona's brother in the back alley-way. Since he has to fire it at such close range, the gun is a flashpaper model during that scene. Later when Chelios goes to the hospital in search of epinephrine, the Desert Eagle changes to the Mark I model, which he fires several shots from before leaving it in the hospital elevator.
Submachine Guns
Heckler & Koch UMP45
One of Don Kim's thugs is seen firing a Heckler & Koch UMP45 during the roof shootout.
Heckler & Koch MP5A3
One of Don Kim's thugs is seen using a Heckler & Koch MP5A3 with a Navy trigger group and M68 Aimpoint scope during the roof shootout. It also appears to have a cover over the M68 Aimpoint scope. How useful is that?
Heckler & Koch MP5A4
Several of the SWAT officers are seen armed with full stock Heckler & Koch MP5A4 submachine guns with surefire light dedicated forends.
IMI Uzi
One of Don Kim's thugs is seen firing a IMI Uzi during the roof shootout.
IMI Mini-Uzi
Several thugs in the film wield IMI Mini-Uzis submachine guns.
Rifles
AKMS
While Doctor Miles (Dwight Yoakam) describes "Excitement, fear, and danger", the image in the middle reveals a hooded terrorist holding an AKMS. The terrorist is a cameo role for the weapons armorer of the film, Guillaume DeLouche.
AKMSU
One of Don Kim's thugs is seen firing an AKMSU during the roof shootout.
M4A1
The SWAT team responding to the shootout on the roof are armed with many M4A1 rifles with the carry handles removed, although some of them have no back sight added.
Shotguns
Sawed-off Double Barreled Shotgun
One of the thugs in the textile mill is armed with a Sawed-off Shotgun and tries to fire it at Chelios, who uses Kaylo's (Efren Ramirez) dead body as a shield from the shots.
Serbu Super Shorty
One of Carlito's thugs uses a Serbu Super Shorty during the roof shootout.
Mossberg 500
When Chelios goes to visit the man in his pool, a guard on the roof is armed with a Mossberg 500 shotgun fitted with a saddle mounted spare shell holder.
Later during the textile mill shootout and car chase, one of the thugs is seen wielding a pistol grip Mossberg 500, likely a Persuader model.
Mossberg 590
One of the SWAT officers is seen armed with a Mossberg 590 shotgun with a surefire light dedicated forend.
The thug on the rooftop with the AKMSU pulls out an M26 hand grenade to throw at Carlito's men on the roof. Carlito then uses one of his own men to deflect the grenade.
Extra (Note)
While this has nothing to do with guns, I figured this was worth noting. At the end of the film when Chelios and Verona fight in a helicopter that seems to fly up to about a 1000ft in the air, Chelios falls out and leaves one last message on his girlfriend Eve's phone. Somehow the wind that would be rushing past his phone does not interfere with the call in anyway, even though in real life the call would be inaudible.
At one point in the sequel, we hear the message is nothing but wind, despite the fact we hear it clear as day on Eve's message machine. Although, this was likely the way Chev was imagining it would hear.