The Ruger KP90 is the apparent standard-issue sidearm of Omega Sector, Harry Tasker's (Arnold Schwarzenegger) association, being carried by him, Albert "Gibb" Gibson (Tom Arnold), and Faisil (Grant Heslov) in many scenes. Tasker notably uses it when combating Salim Abu Aziz (Art Malik) in the bathroom and the proceeding chase through Central Park and the Marriot hotel.
Glock 19
In the beginning of the film, Harry Tasker (Arnold Schwarzenegger) uses a Glock 19 pistol to shoot the guards pursuing him from the mansion. In the script, the gun was classified as a Glock 21 (The script called it a .45 ACP), but it was changed to a Glock 19 for the film, likely due to the larger magazine capacity. He was supposed to use the Glock throughout the whole film, but he instead uses a Ruger KP90.
Makarov PM
During the bathroom scene, Yusif (Ofer Samra) attempts to kill Tasker (Arnold Schwarzenegger) with a sound suppressed Makarov PM, but thanks to the camera in the fake cigarette package on the bathroom sink, he is able to see the attack coming from his glasses, and avoids the shot, and he then disarms Yusif using it.
Daisy Model 93 air pistol (S&W 659 replica)
In the briefcase of Simon (Bill Paxton), Helen Tasker (Jamie Lee Curtis) finds what appears a pistol that closely resembles a Smith & Wesson 659. Later, the pistol appears to have been a Daisy Model 93 air gun.
Beretta 92FS
Tasker (Arnold Schwarzenegger) pulls a Beretta 92FS to interrogate Simon (Bill Paxton). One of the Crimson Jihad terrorists that captures Tasker and Helen is also seen armed with one.
Beretta 92SB-C
Juno Skinner (Tia Carrere) carries as her sidearm of choice a Beretta 92SB-C. She uses it to hold Helen Tasker (Jamie Lee Curtis) hostage in a limousine and they struggle for it; a stray shot fired during the brawl kills the driver and sends the limo out of control on the bridge in Florida.
One of the terrorists carries a Heckler & Koch P9S while guarding Harry (Arnold Schwarzenegger) and Helen (Jamie Lee Curtis) in the torture chamber. Harry also takes the pistol after the guard has an encounter with a meat hook.
Browning Hi-Power
One of the terrorists that captures Harry and Helen is armed with a Browning Hi-Power.
Janice (Jane Morris), the receptionist at the Omega Sector, has a cocked-and-locked Taurus PT99 strapped to the bottom of her desk in a paddle holster, should an enemy attempt to break into the facility.
Desert Eagle
While never seen in use, a Desert Eagle of unknown model is seen in Harry Tasker's (Arnold Schwarzenegger) shoulder holster when he is being X-Rayed by his agency's security system.
Submachine Guns
MAC-10
While fighting their way through the Crimson Jihad camp, Harry (Arnold Schwarzenegger) hands Helen (Jamie Lee Curtis) a MAC-10 he took off a terrorist. In one of the film's more humorous scenes, Helen drops the weapon down a flight of stairs causing it to go off when it hits each step, the stray rounds scoring several kills. This scene was re-created on Mythbusters and thoroughly debunked.
Heckler & Koch HK94A3 (chopped & converted)
When Tasker (Arnold Schwarzenegger) and several other agents capture Helen (Jamie Lee Curtis) and Simon (Bill Paxton) for interrogation, they are armed with Heckler & Koch HK94A3s chopped down and converted to full-auto fire to resemble Heckler & Koch MP5A3s. They are also seen in the hands of the SWAT team members escorting the news reporters to the terrorists in the skyscraper.
Heckler & Koch SP89
The guards pursuing Tasker (Arnold Schwarzenegger) at the beginning of the film are armed with Heckler & Koch SP89s mocked up as MP5Ks by adding MP5K foregrips and converting them to full auto fire. A number of the SP89s were fitted with attachments at the pistol grip for fitting Maxabeam lanterns.
TRIVIA: The actor playing the terrorist, Max Daniels, later appeared in Heat, in which he played a bad guy who gets killed by Robert De Niro while also firing a Steyr TMP.
Cobray M11/9
Many terrorists in the film are seen wielding Cobray M11/9 pistols, converted to full auto and some fitted with wire stocks.
IMI Uzi
An Uzi is briefly seen in the hands of a terrorist following Aziz (Art Malik) when he goes to meet Tasker (Arnold Schwarzenegger) after him and his wife are captured by the faction.
Rifles / Carbines
Custom Shortened AKMS
Salim Abu Aziz (Art Malik) can often be seen using a Custom Shortened AKMS with two magazines taped together "jungle-style" as his primary weapon. It appears to have had the barrel professionally shortened to compact status, and clearly uses the hooded Norinco front sight, as well as other parts from both the Norinco Type 56 and the AKMS.
AKM
A weapon heavily used by the Crimson Jihad terrorists is the AKM assault rifle. Tasker commandeers several AKMs as he makes his escape from the terrorist's camp.
Colt AR-15 Sporter II Carbine (mocked up as XM177E2)
Some of the men guarding the mansion at the beginning of the film are seen armed with Heckler & Koch HK91A3 rifles, as noted by their collapsing stocks.
Shotguns
Ithaca 37
A Miami-Dade police officer is seen aiming an Ithaca 37 shotgun when the remains of a terrorist helicopter crash down on top of a police cruiser.
Other
Mk II Hand Grenade
At one point in the film, Tasker (Arnold Schwarzenegger) uses a Mk II Hand Grenade to kill several terrorists. For those wondering where this grenade came from, it was originally in the script that Juno put a grenade between Helen's legs, saying all she has to do is keep her legs closed, which Helen remarks is a problem Juno seems to have. When the two escape, Harry re-pinned the grenade using Helen's diamond earring for use again later. This was cut from the film, causing this grenade's presence to appear to be a continuity error, however the scene remains in the True Lies novelization by Dewey Gram & Duane Dell'Amico. This grenade, complete with the earring in place of the pin, is prominently visible on many of the posters for the movie and on the region 2 DVD cover.
M72A2 LAW
At the end of the firefight in the Crimson Jihad camp, Salim Abu Aziz (Art Malik) uses an M72A2 LAW to try to kill Harry Tasker (Arnold Schwarzenegger), although Harry is able to escape the blast by diving into the ocean.
FIM-92 Stinger
When the USMC Harriers are cleared to destroy the trucks the Crimson Jihad and the nukes are traveling in, one of the terrorists attempts to shoot down one of the planes with an FIM-92 Stinger, but another terrorist is blown out the windshield of the truck by the backblast.
M60 Machine Gun
Near the end of the film when Tasker (Arnold Schwarzenegger) goes to rescue his daughter Dana (Eliza Dushku) from the terrorists in a Marine Corps Harrier, some terrorists flying by in a helicopter fire a door mounted M60 machine gun modified to use a brass catcher at the aircraft, and shatter the front of the cockpit's windshield while Tasker is trying to grab his daughter as she hangs from a construction crane. The M60 machine gun had the fore-end removed and the catch bag mount installed to use the brass catcher on the M60 but retained the standard butt stock and trigger group.
General Dynamics GAU-12/U
When Tasker (Arnold Schwarzenegger) takes off in a Marine Corps AV-8B Harrier II jet, he uses its General Dynamics GAU-12/U 25mm rotary cannon to great effect when demolishing the 23rd floor of the skyscraper, and later uses it again in his attempt to shoot down the terrorist helicopter. U.S. Marine pilots are previously seen also using the weapon to destroy a truck being driven by Crimson Jihad terrorists on the Key Bridge.
Three real, armed USMC Harrier IIs of Marine Attack Squadron 223 (VMA-223, "Bulldogs") participated in the filming for a fee totalling $100,736: two aircraft, WP-03 and WP-16, are identifiable in the film, with the third presumably hired in case something went wrong with the other two. In scenes where Schwarzenegger is shown flying the plane, though, it is instead a full-size fiberglass replica with no working parts aside from the acetylene-powered guns: the canopy and landing gear of this replica are spare parts from a real USMC Harrier II. This prop was variously shot on a soundstage with greenscreen effects and filmed on location, in the latter case being puppeteered from a crane on one of the nearby buildings which was painted out with CG in post-production.
The prop aircraft was left in the desert after filming wrapped to preserve it and was essentially abandoned until being recovered and refurbished for the filming of The Avengers in 2012: it is the aircraft that Hulk lands on when he is knocked back by Thor during the fight scene on the Helicarrier. Following this it was purchased and repaired by the Volo Auto Museum in Illinois, where it is currently on display.