This post is just my opinion about a specific model. I wasn't looking to start a discussion on the relative merits or draw backs of having a light mounted to a weapon. ( as an LEO I personally am in favor, YMMV)
Surefire has the X200 series that are nice small and bright. Problem is not everyone afford $200.00 for a light.
I just picked up the Streamlight TLR-1. It's a bit larger than a Surefire model . It uses a reflector and a 3w LED. Of the 2 I have handled both have had nice white tints to the LED (sometimes you get blue, sometimes cat urine green). Streamlight seems to be using a decent "bin" on the LED. Run time is rated at 2 1/2hrs on a set of CR123 batteries.
This sucker is bright, easily in a class with any 6v incandesant "tac" light. It pretty much matches my Gladius in ouput. Since it uses a reflector rather than an optic you get a nice central hot spot with HUGE side spill. The level of light is rated at "up to" 80 lumens (LED"s have variable's that determine output). being an LED you have no lamp to fail under recoil or burn out. It is more than adequate for it's primary intended use of being pistol mounted. It would also be excellent mounted on a shotgun.