Runaway

Guns used in this Sci-Fi movie:

Detonics Servicemaster/Combatmaster

Used as a service handgun by Tom Selleck and Cynthia Rhodes. The gun has the characteristic Detonics forward mounted rear sight, which was featured on the combat master, but the longer grip frame of a Service master. It should also be noted that there is a line present on the slide where a combat master slide would end, a similar gun can be seen in Terminator 2: Judgement Day)

Ramsay and his new partner head into a cornfield to stop a runaway

Ramsay uses a Detonics in "Runaway"

Ramsay takes control of a suspect who left his child at the mercy of a runaway

Thompson holds a hotel room full of suspects at bay with her service issue detonics

Detonics Combatmaster

In the third act of the film, while trying to protect Jackie Rogers from Luther both officers use compact combat masters as sidearms.

Ramsay gives up his gun to Luther for the second time

Ramsay takes cover from explosive projectiles while patrons of the outdoor cafe wonder why

Smith & Wesson Model 19

The 2.5"-barrel version is used by a robot (!)

S&W 19 in "Runaway"

Missile Pistol

Though the model info is unknown, the missile-firing pistol used by the villain, Charles Luther (Gene Simmons), in the movie, was probably designed by the prop department. Interestingly, the publicity materials for the film, chiefly the poster, showed Tom Selleck holding the gun though he never uses it in the movie. The story alludes to one of the scientists working with Luther being an expert in propulsion & perhaps the supplier of the gun & its ammo. The runaway squad's chief tech officer (Stan Shaw) later calls the mini-rockets "smart bullets."

The projectiles are all electronic "heat seeking missiles" with a back half made up of solid propellant, making use of valves for directional control. They are able to be programmed to "go after" a specific person using a person's unique heat pattern as a signature.