laser sight

A detachable, rectangular laser module mounted to a firearm which projects a colored beam onto the target, improving the shooter's accuracy. Also see laser pointer projection, which can be used when the beam and/or dot are visible.

Not to be confused with laser pointer, a small cylindrical tool used to direct attention to one spot during meetings and lectures.

Also please don't confuse with eye beam, where lasers may shoot from a character's eyes.