Stun Gun is an electroshock weapon used by the Galactic Patrol to incapacitate a target.
It delivers an electric shock aimed at temporarily disrupting muscle functions and/or inflicting pain without causing significant injury. The stun gun has a design virtually identical to the Elite Beam Gun used by Galactic Patrol members though the Stun Gun is a non-letal weapon.
Merus used this to incapacitate Goku and Vegeta when he attempts to stop him and the Galactic Patrol from taking Good Buu during the Galactic Patrol Prisoner Saga. Merus used it to knock out the Saiyans to avoid a fight as he needed them to deal with the escaped Planet Eater Moro. The Stun Gun is extremely effective as it is capable of incapacitating God-like Saiyans.