I like both Streamlight and UK plastic AA LED lights. Both make a couple of versions, most are rated to be safe in an explosive atmosphere. These are my picks because they're very rugged and safe, the plastic is comfortable to use in either very cold or hot weather, they use common batteries, and because they're light they don't cause themselves any damage if dropped at normal heights.

Of the two, I like the streamlight beams better, but like the UK build quality *slightly* better. It's neck and neck, though. I carry a 4AA LED UK in the glove box, and a 4AA LED Streamlight in my radio bag. I have a bracket to clip the UK to a hard hat. I believe both companies make brackets for hard hats and fire helmets. Some of the UK lights are dive rated, but the explosive rated lights of both makes are very waterproof.

One good place to shop for lights is:

http://www.brightguy.com/shop.php

No connection to me, just a company I've bought things from. They carry Steamlight, UK, Surefire and lots of others.

Personally, I like a light that goes off and on, no focus, no funny flashing modes or dancing or singing involved. One less thing to deal with or think about, one less thing to break.