The Ray Gun is an extremely powerful gun. It shoots out red magic, and almost always kills with one shot. In Super Scribblenauts, it has infinite ammo, and coupled with the fact that it is so powerful, making it a first choice of weapon for most players. Also in Super Scribblenauts, if you change the color of the Laser via adjectives, the projectile changes color too.
In Scribblenauts Unlimited, it is much weaker, and fires @Laser Beam instead of red magic. Also, ( In Scribblenauts Unlimited )the synonym "Death ray" spawns a Death Ray, which is capable of destroying anything and everything one shot.