As in all the previous Lethal Weapon films, Detective Martin Riggs (Mel Gibson) carries a Beretta 92FS as his weapon of choice, albeit this time fitted with Crimson Trace grips with integrated laser pointer. At one point in the film, the pistol is rendered unusable when the lead villain, Wah Sing Ku (Jet Li), manages to field strip the pistol through crafty manipulation of the takedown lever although he seems to have reassembled it afterward because he is seen wielding it in the final shootout and at the end.
At the beginning of the film, Riggs and Murtaugh respond to a call of a "Human Tank" dressed in a fireproof suit wreaking havoc with a flame thrower and an OA-93.
What is interesting is that there is a small "pistol" buffer tube attached to the upper receiver of the OA-93. This feature is not part of the OA-93 design, which has a distinctive recoil assembly above the upper receiver which eliminates the need for a buffer tube with spring. Movie armorers had difficulty making the OA-93 cycle blanks, so they added the small buffer tube to the back of the gun, however the original gun doesn't have a buffer tube.
As in the previous two Lethal Weapon films, Detective Murtaugh uses a Smith & Wesson 5906 as his back-up weapon. Detective Riggs also brandishes this weapon during the encounter at Murtaugh's house.
During the encounter at Murtaugh's house, one of the Chinese triad gang members, Fan(George Cheung) can be seen with a Glock 17, Lorna Cole (Rene Russo) later manages to get the weapon away from him.
What's that on the trigger guard in the last two screenshots?
most likely another laser aiming device.
Flamethrower
At the beginning of the film, Riggs and Murtaugh respond to a call of a man dressed in a fireproof and bulletproof suit wreaking havoc with a flame thrower, torching anything that comes near.
Leo Getz(Joe Pesci) has a Colt Commander that he has acquired as he has become a "private detective". He tries to shoot a shark they caught on Murtaugh's boat before Riggs takes it away and throws it overboard.
In several scenes, a rookie officer, Detective Lee Butters (Chris Rock) can be seen wielding a stainless steel Gold Cup National Match M1911A1 as his standard weapon.
Several members of the Chinese triad can be seen wielding Makarov PM pistols, most notably during the encounter in Murtaugh's house. From closer examination of the pistols, it appears that the Makarovs used by the triads were Chinese-made Norinco copies of the Makarov PM.
When Riggs & Murtaugh reveal that the money being paid to the Chinese General is counterfeit he flips out and kills one of the 4 fathers with a Beretta Cheetah before being killed by Triad members.
Several of the General's men use them as well.
Near the end of the film, a three-way gun battle erupts between the protagonists, Chinese triad members, and the private army of a corrupt Chinese General. The General's men can be seen wielding MPi-KMS-72's, one of which Riggs gets ahold of to kill Wah Sing Ku (Jet Li), firing the weapon point-blank while both of them are underwater.
