Used by the security guards at the subway station, the Mars Colonial soldiers, Richter (Michael Ironside) during the shootout at the Last Resort strip brothel and Cohaagen (Ronny Cox) at the end of the film.
Used by Quaid, Melina, and the Mars Federal Colony troops throughout the film. The firearm consists of a Ruger AC-556 automatic rifle being fitted into a modified Muzzelite bullpup stock (the stock has the foresight section removed). Along with the removal of the foresight, the firearms had their barrels shortened and the the firearm fitted with a small tactical scope on the carrying handle section.
Several heavily modified SWD/Cobray Street Sweeper shotguns are used by Mars Federal Colony troops, as well as Richter (Michael Ironside) during the car chase through the Martian tunnels. It is modified using an M203 Handguard, M1919 Barrel Jacket and is probably intended to resemble the Pancor Jackhammer shotgun.
Several of Richter's goons can be seen using modified Micro-Uzis at various points in the film. Richter's right-hand man Helm (Michael Champion) uses one with half nickel-plated parts fitted with a flash-hider. This is the same weapon from The Running Man.
Many of the bad guys use an Uzi modified with a hand guard and barrel extension to make it look sci-fi. I'll upload an image soon.
Heckler & Koch MP5K submachine guns were seen in the hands of the Kuato's resistance fighters and the residents of Venusville. Melina (Rachel Ticotin) is seen with one with the foregrip removed.