Maglite's uses commen batteries, but really don't give much light for it's size, has a ugly beam (although focus-able), very bad discharge curve (they only seem to give good output with fresh batteries and quickly become much dimmer for a long long time...)
You'll be interested in Maglite's LED flashlights and conversion kits. Apparently with some of the multi D cell flashlights you can run an LED for a couple of months continuously!
I bought a 3-watt no name flashlight off E-Bay last week. It's brighter (60+ lumens) than my 2-D cell Maglite. Great deal - I only paid 11 cents for it. <img src="/images/graemlins/shocked.gif" alt="" /> It's maybe 20% of the size and weight for more light. EGGCELLENT! The one downside - since it is a no name flashlight, it doesn't appear to have a regulating circuit so the light output will fall off fairly quickly after the first couple of uses. It has a very bright spot and a secondary wider cone of light that is very white and much more useful than the variable bulb of the Maglites I own. (One 2-D cell, two 2-AA cell lights)