Billy (Sonny Landham) and Dutch (Arnold Schwarzenegger) are prominantly seen armed with AR-15/SP1 slab-side M16 rifles fitted with M16A1 birdcage muzzle flash suppressors to apear more modern (they are likely AR-15/SP1s over genuine M16s, converted to full-auto by the armorers for the film). Dutch's AR-15/SP1 is fitted with an Fake M203 Launcher and a perforated forend typical for the M203, while Billy's AR-15/SP1 is fitted with a Mossberg 500 shotgun and M16A2 foregrips. These particular SP1 rifles are clearly fitted with blank adapters (which are visible sticking beyond the muzzle, out into the flash hider), which means they were real guns converted to fire blank rounds. Many other guns in the movie also have these adapters visible.
Fake 39mm M203 Launcher
Fitted on Dutch's AR-15/SP1 is a Fake M203 Launcher with a 39mm bore diameter. This particular faux launcher was popular at the time before the Cobray launcher was produced and was used in several other '80s movies, including Heartbreak Ridge. Gun is inaccurately seen as capable of detonating its rounds at close range, yet real M203 rounds have a safety device in which they must spin for a certain amount of time before detonating, giving it a range limit. Dutch later uses his spare 40mm rounds (which actually don't fit his launcher) to make explosives to face the Predator.
Mossberg 500
Billy's AR-15/SP1 is fitted with a Mossberg 500 underslung under the barrel. While never seen firing the shotgun in the film, he is seen pumping it closed after the men cut down the forest with weapons fire, implying he had been firing it during that scene. In the original screenplay, Billy's SP1 rifle was to be fitted with an M203 launcher. During the helicopter scene, he was to be seen opening and closing the breech repeatedly. Since the fake M203 launchers don't open in such a manner, I guess someone decided to change it to a Mossberg 500 shotgun (although they seemed to have forgotten the helicopter scene).
M60E3
An M60E3 machine gun is carried by Sgt. Mac (Bill Duke). Like the gun in Commando, this M60 appears to have a professionally shortened barrel. They actually could be the same gun supplied by Stembridge Gun Rentals.
GE M134 Minigun Handheld
Nicknamed "Old Painless", a hand-held M134 Minigun is the main weapon of the movie carried by Blain (Jesse Ventura). It has been modded for Commando use with an M60 handguard and a rear pistol grip. The weapon was powered by an electric cable hidden in the actors pants and fired reduced power 7.62x51mm blank rounds to ease the recoil force. It is believed in real life a similar weapon was tested by US special forces in the 1970s but found impractical. Although rumored to be an XM214 'Six-Pack' which fires the smaller 5.56mm NATO rounds, it is the larger M134 hence the barrel cluster.On the subject of the weapon's caliber the film's technical advisor Kevin Dockery had the following to say."The Predator gun is an M-134. It was never a microgun (XM-214). That story has been rattling around the Internet and elsewhere for years, that the Predator gun was a 5.56, it wasn't. Ventura had a hand in putting together the harness that held the gun, after all, he had to carry and handle the darn thing, and told me a bunch about it. When Dan had the gun (past tense I believe) he contacted me to see if Ventura wanted to buy the weapon. I'm going to do a writeup on the XM-214 including pictures of me holding one. It isn't a big deal to pick the microgun up and hold it cradled in one arm. Maybe when people see just how small the 5.56mm gun is, this story will start going away. The pack in the movie held all of four seconds worth of ammo and no batteries. In the first scene when Ventura fires the gun, you can see the cable for it in the dirt behind him. And the trigger didn't work. The special effects man handled powering the gun for several reasons, including safety. Something about them not wanting the actors injured if the gun was dropped and the trigger pulled." The gun is also operated in the film by Mac shortly after Blain's death and Mac uses it to chop down half the forest in an attempt to kill the Predator. In the film, the Minigun is seen firing between 1700 and 1800 rounds per minute. Normally GE Miniguns at this time had two fire rates of 2000 and 4000rpm. For the firing scenes, the weapon is fed from the same type of helicopter ammo box used on the M23 armament system for the M60D machine gun. This gave him a capacity of 550 rounds, about 1/3 of the ammo needed for the 58 seconds of on-screen firing. For the non-firing scenes the ammo box was turned on its side with the chute attached to the bottom of the box and positioned upside down on the gun in order to hide the fact that there was no ammunition present.
GE M134 Minigun
One of the Bell UH-1N helicopters that drops the men off has a door-mounted GE M134 Minigun.
Heckler & Koch HK94 (chopped and converted)
The Heckler & Koch HK94 are the mainstay weapons of many members of the squad. Blain (Jesse Ventura), Poncho (Richard Cheves), Hawkins (Shane Black) and Dillon (Carl Weathers) all carry them. The guns are meant to be MP5A3s, but close inspection reveals they are the civilian HK94s with the 16" barrels chopped down and they are converted to full auto. They clearly aren't MP5A3s due to the lack of the three lugs on the barrel, the lack of the paddle magazine release situated behind the magazine, under the gun. They also lack the push pin set.
Custom 37mm Launcher
A custom launcher built specifically by the armorers is used by Poncho. It is built from Heckler & Koch HK94 parts (mainly the stock and pistol gips) and uses parts ftom an AN-M5 aircraft pyrotechnic discharger (a 37mm flare launcher). Its possible the same launcher was used in Braddock: Missing In Action 3.
M18A1 Claymore
Sgt. Mac can be seen arming M18A1 Claymores as part of the defensive perimeter when he and the commandos camp out for the night after Blain is killed, then when Dutch orders the other commandos to make a stand against the Predator in the jungle. Mac and Blain are also seen disarming a Claymore when they sneek into the Guerilla camp.
Walther PP
One of the Guerillas is seen using a Walther PP to execute an American prisoner. Anna (Elpidia Carrillo) is also seen trying to shoot Dutch with a Walther before he whips around and rifle butts her.
IMI Desert Eagle
Billy, Dutch, and Mac are also seen with IMI Desert Eagle handguns, presumabley .44 or .357 Magnum, holstered as their sidearms. Dutch keeps his in a hip holster while Billy and Mac use shoulder holsters.
M1911A1
While the other Commandos have more modern pistols, Dillon is briefly seen with an M1911A1 pistol as his holstered sidearm.
AKM
Some of the Guerillas fighting the commandos are armed with AKM assault rifles.
Valmet M78/83
Some of the Guerillas are seen armed with Valmet M78 light machine guns, note by their synthetic "Dragunov" style stocks. While similar to an RPK machine gun, slight differences in the sights and receiver help tell them apart.
M67 "Baseball" hand grenade
Dutch uses an M67 hand grenade to start the battle between the Guerillas.
Satchel Charge
Dutch plants a Satchel Charge on one of the Guerilla trucks and then uses his hulk-like strength to roll the truck into a cluster of them.
Custom Torque Bow
When preparing to fight the Predator, Dutch builds himself a recurve bow with enough strength to send arrows completly through trees. Dutch also builds some explosive tipped arrows with no visible ignition source, so apparently they just explode on impact for no reason.
"Blow Dryer" Gun
The infamous shoulder mounted plasma gun used by The Predator (played by 7'2" tall actor Kevin Peter Hall, now deceased), nicknamed the "Blow Dryer" gun due to its similarity to a Hair Dryer is used several times in the film and is the main cause of death to many of the team's Commandos.
"Plasma Caster" is another name commonly attached to the shoulder cannon.
Harpoon Gun
Before the great Stan Winston (RIP) turned the Predator into what it was, it was originally going to use a Harpoon gun, and in one scene, we see this gun's projectile in use. The Predator uses it to skim Blaine's shoulder and stun him before using his shoulder gun to put a hole through his chest. Since this idea was dropped, this is the only instance the weapon is seen used in the film.
There is also the possibility that the Harpoon could be another version of the "Spear gun" seen in the second movie.