This looks like an Earth gun, made of hard, shiny brown plastic, with a wide barrel.  When the trigger is pulled, an invisible beam comes from the muzzle.  If it hits you, it jars your nerves, causing great pain.  If it hits your head or body, the pain is so great that it knocks you out, for up to ten minutes.

Criminals (eg Hallixian pirates) use nerve-guns, but agents must have special permission to carry them – usually to use against animals that are not knocked out by a stun-gun.