I'll second most of what James V A said. The ability to use lithium batteries is important if you're going to depend on the flashlight. They'll work in hot and cold extremes that will kill a regular battery. The looooong shelf life is another plus.

I'll also second the NovaTac recommendation. I have an HDS U60 that is one of my favorite lights. I use it regularly (5 to 10 minutes 5 days a week) and get 6 to 8 months out of a single battery.

Something else to keep in mind is the wild lumen claims from most flashlight manufacturers. Surefire, Arc, and Novatac (that I can think of right now) are the only lights that are rated with lumens out the front. If you have a Surefire that claims it's putting out 60 lumens, it's putting out 60 lumens that you're seeing after exiting the lens. Most everybody elses lumen claims are at the peak efficiency of the LED before transmission losses through the lens and an extra pinch of exaggeration. An example is my Arc AAA-P that is rated for 5.5 lumens that is slightly brighter than another light I have that claims 20 lumens and as bright as one that claims 25 lumens.