A Repulsor is a particle weapon designed and built by Tony Stark. It was originally designed simply as a flight stabilizer for the upgraded flight capabilities of the Mark II, as it could effortlessly generate enough force to defy gravity and weight. Stark found that the forceful blast from the device could be used as concussive energy weapon, designed to physically repel targets and exert enough extreme amounts force to blast though stone and metal or break it apart. It also could manifest with intense heat, enough to burn through metal. With the introduction of the Mark III, the Repulsor demonstrated that it could be focused into an energy beam. Becoming the primary weapons used in the Iron Man armor, they have been used in every version. They can be fired in small, concentrated, single bursts, or sustained in a high energy ray. The sixth armor could even reduce the repulsors into welding beams, allowed him to install an Arc Reactor for Stark Tower.
Repulsors were first introduced in Iron Man's Classic armor (the name given in the official video game) and has been used in every armor created since. Repulsors have also been integrated into the Insight Helicarriers, only used to achieve and sustain flight, and Stark's Iron Legion drones that appear in Avengers: Age of Ultron.