I often get questions about laser gun sights.  These devices either fit under the barrel; attached to your dust cover rails, inside your Glock; replacing the guide rod/recoil spring, or on the grip.  There are a handful of manufacturers and they all make outstanding equipment.  They all perform very well, they all have their quirks.  They are all tough and compact and are really remarkable innovations.
Unfortunately, I think they are all totally inappropriate for civilians.  A Police officer I once interviewed told me that they will use their laser-equipped Glocks to intimidate perps into compliance.  Just like a movie sniper, law enforcement shines that bright red (or green now too) dot on the forehead to frighten badguys onto the ground where they can be handcuffed by another officer.
 
That’s swell for cops.
 
Here’s the difference.  If you draw your gun, you better be well past the ‘scare-him-into-submission’ phase.  If not, it will just as likely be you in cuffs.  Drawing a gun to scare someone away is brandishing in most cases and is a crime.  In the time it takes you to fiddle with your gun to get the laser to come on, the badguy should already be bleeding out on the floor.  While law enforcement can use their firearms for whatever they want, you can only use yours to end a threat of imminent death or great bodily harm.
 
If you need a red dot to instruct you on where the bullet’s going to go, you need more training.  If it’s dark enough for you to see that red dot, you need a flashlight.
 
Carrying and using a gun is not a game that you win with technology.  You don’t need expensive accessories to put bullets where you want them.  You need training and practice.  Spend your money getting trained and shooting.
 
Leave criminal psychology experiments to law enforcement.  Your job is to keep you and your family safe, not to spare the lives of badguys by giving them a chance to reform before your awesome technology.