As in Die Hard 2, NYPD Lt. John McClane (Bruce Willis) carries a Beretta 92FS as his sidearm. The Beretta is first seen as it is given back to McClane once he is reinstated. He uses it several times throughout the movie, most notably pulling it when surrounded by Simon's men in an elevator and firing it while driving a Mercedes to kill a pair of pursuing terrorists in a pickup during the film's car chase on the L.I.E. Katya (Sam Phillips) also uses a Beretta to fire at a helicopter overhead.
The security guards at the Federal Reserve Bank of New York appear to carry Glock 19's. The terrorists that McClane shoots in the elevator are also armed with Glock 19s.
When Simon and his men steal the gold out of the Federal Reserve Bank of New York, one of the security guards can be seen loading up a Mossberg 500 with a heatshield and firing it at and missing Simon and his men before he is killed by Katya.
A common weapon seen used by the terrorists are Heckler & Koch MP5K submachineguns. During their infiltration of the cargo ship, John McClane takes one off of a dead terrorist and gives it to Zeus Carver before sending him off to find Simon Gruber. When Zeus does, he corners Simon and threatens to kill him if he doesn't give out the code to disarm a school-planted bomb (later found to be a decoy). Simon refuses and Zeus pulls the trigger, only to find the gun on safe. Simon disarms him, notes the fact that the safety is on, and then shoots Zeus in the leg.
John McClane lifts a MAC-10 off of a dead cargo ship terrorist after his fight with Targo (Nicholas Wyman), taking it and the Beretta up to the bridge, where, after discovering that the bomb they were chasing after is on board the ship itself, he is disarmed by Simon Gruber and his men.
While preparing to depart the doomed cargo ship, Simon Gruber and Katya are confronted by Targo, who discovered earlier what was really the cargo on the ship. After Targo accuses Simon of betrayal, Katya draws a nickel-plated Walther PPK/S with pearl grips and empties the magazine into Targo, killing him.
During the shootout at the border, Simon Gruber uses an M60 machine gun from the seat of a helicopter to shoot at a nearby chopper carrying John McClane and Zeus Carver.
When McClane is forced by Simon to go into Harlem, a nickel Smith & Wesson Model 36 revolver with Pachmayr grips is taped to his back. Zeus Carver (Samuel L. Jackson) steps in and grabs the revolver off McClane's back, using it to intimidate the assembled mob into backing off long enough for the two to escape.
During the shootout at the Canadian border, John McClane uses the pilot's standard Smith & Wesson Model 36 revolver while under attack from Simon Gruber.
Another frequently-used weapon by Simon's men is the Uzi sub-machine gun. It is most notably seen in the scene where Targo rigs the dam to blow in an attempt to drown McClaine as he's pursuing them.
Just before they blow the dam, one of Simon's men can be seen with what appears to be a Bushmaster XM15E2 of some sort. Bushmaster built the AR15s for the movie and for Bruce Willis' personal collection. A Bushmaster also appears to be the sniper rifle used by one of Simon's men at Yankee Stadium. Thaat rifle fitted with a suppressor and a spotter's scope.
