I know there are a hundreds of lights out there and you can spend $100 bucks or more on a light depends on what your looking for. Here are some affordable options that use AA batteries. For longer run times your going to have to get lights that run on CR123A or propritary batteries.
Pen light great for when you need a light in tight spaces. It fits anywhere you can put a pen. Small enough that in a pinch you can hold it with your mouth to free up both your hands draw back is that it's only good for up close work and uses hard to find AAAA batteries.
[ame="http://www.amazon.com/Streamlight-65018-Stylus-4-Inch-Penlight/dp/B00008BFS5/ref=sr_1_1?ie=UTF8&qid=1331844182&sr=8-1"]Streamlight 65018 Stylus 6-1/4-Inch Penlight with Pocket Clip and White LED, Black: Amazon.com: Home Improvement@@AMEPARAM@@http://ecx.images-amazon.com/images/I/31Iinbk8MaL.@@AMEPARAM@@31Iinbk8MaL[/ame]
Mini Mag Light. everyone knows these lights, can find them anywhere range from $10 - $15. easy to find parts and runs on AA batteries. Bad thing performance drops in cold temps and it's water resistent not water proof.
[ame="http://www.amazon.com/MAGLITE-M2A01C-Maglite-Flashlight-Combo/dp/B0000AS1G5/ref=sr_1_3?s=hi&ie=UTF8&qid=1331844914&sr=1-3"]Amazon.com: MAGLITE M2A01C AA Mini Maglite Flashlight Combo Pack, Black: Home Improvement@@AMEPARAM@@http://ecx.images-amazon.com/images/I/51sO0%2BiAWiL.@@AMEPARAM@@51sO0%2BiAWiL[/ame]
Fenix E21 best bang for your buck. Well built, Waterproof, performs great in cold weather. 2 brightness settings to help with batterylife using standard AA batteries. Drawbacks is that if you set it down on a sloped surface it will roll away from ya and takes some practice turning it on when wearing gloves.
[ame="http://www.amazon.com/Fenix-Flashlights-E21-Flashlight/dp/B0041NE8TG/ref=sr_1_1?s=hi&ie=UTF8&qid=1331843939&sr=1-1"]Amazon.com: Fenix E21 Flashlight: Home Improvement@@AMEPARAM@@http://ecx.images-amazon.com/images/I/31ywUCvLnsL.@@AMEPARAM@@31ywUCvLnsL[/ame]