Dr. Nathan Waldman (Brian Cox) keeps a stainless Walther PPKS with wood grips in his pants, which is later used by Charly Baltimore (Geena Davis).
Glock Pistol
The police officers who mistakenly target Mitch Hennessy (Samuel L. Jackson) carry Glock Pistols, most likely Glock 17s.
Smith & Wesson Model 36 Nickel Plated
Mitch Hennessy (Samuel L. Jackson) carries a S&W Model 36 "Chiefs Special" 5-shot .38 Special revolver that is nickel plated.
Mitch Henessey: "Ya want me to stick it in my pants and shoot my damn dick off?"
Samantha Caine: "Now you're a sharpshooter?"
Colt King Cobra
Colt Gold Cup National Match M1911A1 Pistol
Daedalus (David Morse) packs a Stainless Series '80 Colt Gold Cup National Match - .45ACP in his waistband Daedalus' handgun has Elliason adjustable sights, a mounting rail on the top of the slide for optics, a skeletonized match trigger and hammer and the beavertail grip safety. (thanks to RedJedRevolver)
SIG-Sauer P226 Nickel
Charly Baltimore uses a Nickel SIG P226 pistol - 9mm. She is shown holding a K-Kote (black) SIG-Sauer P226 on the movie poster but she doesn't use one in the film.
Ruger KP94
Timothy (Craig Bierko) has a Ruger KP94 in his waist band, which he uses later to try to kill Mitch Hennessy, when he gives him the option of being killed with either a knife or a gun, reason given for giving Mitch a choice on how he is to be killed is because it is Christmas.
SIG-Sauer P225
Waldman has a SIG P225 pistol which Mitch Hennessy (Samuel L. Jackson) later uses against Daedalus (David Morse).
Smith & Wesson Model 29-2 snub revolver
A thug falls with a large framed snub revolver that is bright nickel. It is not well seen, but I will hazard an guess that is is a 2" S&W Model 29 revolver that is nickel plated. Though seen briefly it is a very large framed revolver and being bright nickel would not be any of the Stainless models.
Beretta INOX
Charly and Timothy fight over a Beretta INOX - either 9mm or .40 S&W.
When Samantha goes through her suitcase at the hotel, she finds a hidden case which contains what appears to be a disassembled Remington 700 takedown rifle. The bolt handle, rear of the receiver are the same as a Remington 700. This rifle is similar to the one used by Dennis Haysbert in Absolute Power.
Mitch Hennessy carries a Winchester Model 1894 lever action rifle - caliber unknown.
Colt 733 Carbine
Bad guys use the Colt 733 Carbine and Charly Baltimore also uses it with a scope at the night battle.
Ruger Mini 14
Charly Baltimore uses a Stainless Ruger Mini-14 with synthetic black stock, heat shield/barrel shroud, Stainless B-Square side-mount scope base & scope, and an aftermarket stainless flash hider.
Winchester 1887 Shotgun with M203 Grenade Launcher
A stranger combo cannot be described. One Eyed Jack (Joseph McKenna) tries to kill Charly Baltimore (Geena Davis) with an M203 40mm Grenade launcher attached to a Winchester 1887 Lever action shotgun. However, in the film, flip cocking the shotgun, somehow reloads the grenade launcher. Also when it fires, the projectile looks more like a guided missile than a grenade. The front foregrip of the 1887 has been removed to allow for the attachment of the M203 launcher.
M16A1
A very strange combination, Timothy while riding in the helicopter, uses an M16A1 rifle to shoot at Charly Baltimore on the bridge, but rather than standard handguards he has the special handguards designed for the M203 combination.
Heckler & Koch 91
One of Timothy's henchmen uses an HK91 rifle in the helicopter when they try to corner Charly and Mitch.
M26/M61 Grenade
Actually a pot metal training grenade, obviously from the markings. This grenade is thrown at Charly and Mitch, and shows all of traits of Hollywood Fantasy grenades. It has a 20 second delay, and packs the explosive power of twenty pounds of C4 and a 55 drum of gasoline.