The S&W 36 is the revolver carried by LAPD Detective Ray Tango (Sylvester Stallone). He uses it in the opening scenes to fire at an approaching big rig that is transporting cocaine. He appears to be able to hit the windshield, and make a tight group, from a long distance, despite the short barrel. He later uses it against Perret (Jack Palance).
Ruger GP101
A Ruger GP101 revolver is carried by LAPD Detective Gabriel Cash (Kurt Russell). It's a stainless steel version fitted with a large 1980s laser sight.
A Beretta 92FS can be seen in the warehouse scene, when Tango (Sylvester Stallone) & Cash (Kurt Russell) are framed, being carried by one of the agents.Additional firearms can also be seen.
Detonics Scoremaster
Tango carries the ScoreMaster as a secondary weapon to his S&W.
Browning Hi-Power
The Browning_Hi-Power can be seen being used by Cash (Kurt Russell). An error can be noticed in the roof scene. Cash pulls the slide back to put a round in the chamber, but the slide stays opened. In the following scene, the pistol is pointed at Requin's leg, but now the slide is locked. In the next scene however, the slide is open again.
Walther PPK/S
A nickel plated Walther PPK/S is Cash's backup gun. It is also the gun used to frame him and Tango. In this occasion, the gun is fitted with a sound suppressor. He mentions that his sights are off in the film, despite the fact that the sights on a Walther PPK/S are fixed to the slide and not adjustable.
A heavily modified Heckler & Koch MP5 is seen used by both Tango & Cash at the end of the film. It's seen fitted with large scope and laser sight and with custom grips.
A Remington 870 folding stock is used by Cash to get the information from audio tech Skinner (Michael Jeter). The shotgun is also used by some of the prison guards when Tango & Cash escape.
Ithaca 37 shotgun
Seen in the hands of an LAPD officer at the beginning of the film.
Unidentified Short Barreled shotgun
A short barreled shotgun is used by the Chinese gunman
Assault Rifles
Colt M16A1 rifle
This rifle can be seen both in the video about Det. Tango and used by some of Perret's guards, as well as in the warehouse.
Ruger Mini-14
Heavy Weapons
Fictional Gatling Gun
The vehicle Tango & Cash "borrow" is fitted with a fictional 30mm gatling gun. Though rotary barrel auto cannons appear all over the world in similar calibers (mostly mounted on gunships) this is a purely fantasy weapon.
M134 Gatling Gun
However, during the final assault, a real M134 minigun is used for firing scenes.
M60D
M60D machine guns are seen mounted on the hood of Perret's trucks that chase Tango & Cash in the gravel pit at the end of the film.
Madsen machine gun
A Danish Madsen machine gun without a magazine is seen when Perret enters his gun warehouse.
Other
Shooting Boots
These boots are used by Cash when confronting the Chinese gunman and when killing Perret.
Unidentified guns
Need some help with these additional guns that can be seen in these images
left: H&K gun(read below), center M16a1?, gun held highest, M60E3, far right AK-47
Smith & Wesson Model 15 revolvers
He's got a Remington 870 folding stock and the others i dont know...
It isn't a big deal if they aren't I.D.ed, they're pretty hard to see.
1911 non-gun
Could also be a Grizzly Win Mag based on the squared trigger guard and size.