The invention relates to an accessory weapon for games and training, with a body (1) provided with barrels (8) and a trigger (2) for firing projectiles (12) with detonation means, the weapon comprising a rail (3) for coupling to the rail of weapons such as pistols or similar, and fastening screws (4). The rail (3) is partial, with a stud (6) for setting the travelling distance thereof or continuous and open at both ends. The front of the accessory weapon has multiple barrels (8) for multiple projectiles (12). The trigger (2) has a shaft (2B) with a limiting screw (9) that determines the movement thereof, activating the detonation means, said means consisting of gas contained in a chamber (11) or a spring and hammers. The trigger (2) can rotate upon itself so that it can be positioned vertically or horizontally.