What kind of gun did Robocop use in the first movie? I know it was a triple burst handgun with a single shot capability.
Beretta 93R (as the "Auto 9")
The primary weapon that Robocop uses in the original 1987 film is the Beretta 93R.
The main weapon used by RoboCop (Peter Weller) is the "Auto 9". This is a Beretta 93R machine pistol which was heavily modified for the film, featuring a longer barrel with an enormous compensator/flash hider shaped like a casket (which apparently made the trademark gun twirl fairly difficult to perform), plastic grips, and a taller rear sight to match the raised front sight. Typically, RoboCop fires this weapon in 3-round burst mode. The fictional stats of the weapon claim it has an implausibly huge 50-round magazine.
Originally it was planned for Robocop to simply carry a Desert Eagle, but Verhoeven felt that the pistol looked too small compared to Robocop's bulky armour, so a special weapon was devised.