Sgt. Joey Bomowski (Sylvester Stallone) is seen primarily using a Taurus PT99. This particular model is a "Long Barrel" due to the extended barrel. Later during the movie Tutti (Estelle Getty) finds the gun and cleans it by using bleach and other assorted cleaning solutions, which in turn removes the bluing from the gun.
Beretta 92FS
A Beretta 92FSs are seen throughout the movie used by thugs and police officers including Lt. Gwen Harper (JoBeth Williams).
Charter Arms .44 Bulldog
While out shopping for a Replacement Taurus Long Barrel, The Gun Clerk (Richard Schiff) attempts to first sell Tutti (Estelle Getty) a Charters Arms .44 Bulldog Revolver for a mere price of $325.
Mitchell (Dennis Burkley) carries a Colt Anaconda on his person, before his rendered unconscious by Tutti (Estelle Getty), who later uses it on Mr. Parnell (Roger Rees ).
H&K MP5K
A random thug carries an MP5K SMG at the airport
Mini Uzi
A thug carries a Mini Uzi with the stock removed at the airport
Colt M1911A1
Mr. Parnell (Roger Rees) is seen carrying a custom nickel-plated Colt M1911A1 with pearl grips, at the films climax, but he never fires it.
Colt Python
A man at the airport pulls a Colt Python, while making his escape from Joey (Sylvester Stallone).
Multiple Pistols
Many pistols are seen in the gun store
I believe the revolver on the far right is a Ruger SP-101, due to the grips
That would be a Walther PPK (Police Pistol Compact), not a PP (Police Pistol-full size). Note the shorter slide and grips. The PP was full size with both, and the slide was longer and slimmer just past where this one ends. The grips on the PP are also longer. Now the PPK/S maintained the short slide and barrel from the PPK, however to meet government requirements, the gun had to meet certain size requirements. To do this, the grips from the original PP were paired with the PPK slide and barrel. This was to become the PPK/S. The pistol shown would be the PPK.
The 1911 pistol shown in the second photo is a standard commercially manufactured Colt 1911A1 Government (Govt length is 5 inch barrel) with factory Colt wooden grips. The 1911 in the first photo is a Colt 1911 Commander with 4 inch barrel.
Multiple Long Guns
Many long guns are seen as well
Unknown Guns
Thugs at the beginning of the film, as well as a police officer all have holstered pistols, which are hard to identify.