From the Super Mario Wiki
Ray Guns are items seen in the Super Smash Bros. series.
In the original Super Smash Bros., the Ray Gun takes the appearance of a small, gray gun capable of shooting lasers. The lasers travel quickly, with an audible bang, and deal low damage; however it is very easy to juggle opponents with timed blasts from the gun. It has enough power for sixteen shots, after which the Ray Gun becomes almost useless, only able to cause damage when thrown.
The Ray Gun returned in Super Smash Bros. Melee, with its appearance upgraded to a more futuristic look. The lasers travel more slowly, though they do the same amount of damage. There are still sixteen shots in a Ray Gun. Also, the loud bang accompanying the shots is replaced by a more laser-like sound.
In Super Smash Bros. Brawl, Ray Guns remained largely unchanged from their Super Smash Bros. Melee incarnation, aside from their appearance, which is much more highly detailed. They still fire their characteristic green shots and still have sixteen shots.
 Trophy Information from Super Smash Bros. Melee
 Trophy Information from Super Smash Bros. Brawl