My Dad works as a LEO, he caries a Streamlight Stinger HPXT. He's not much of a flashlight freak but likes the small size, bright light, and rechargeable battery.
He said that where he works the Streamlight Stinger is by far the most popular light, and that almost everyone uses a rechargeable. He said that most guy's also carry a small light (mag AA for example) for searching small area's. They also like the Streamlight stylus in red or blue for those times when turning on a bright light can get you hurt.
Some guys also like the Mag's and Mag chargers, but mostly because of it's potential as a self defense weapon.
Interestingly his department regulations say that the light has to be less than 11" in length and must be black.