I agree with the headlight LED lamp, will make things easier when you gotta do car repairs in the dark. I have the entire collection of Maglites, from 2D to 6D, and I like all of them. The 6D does make a formidable weapon, and if you upgrade it with the Malkoff light module, it's light output is impressive. I live out on 40 acres, and I can easily light up cows' and coyotes' eyes past 200 yards when it's focused. Maglite does sell an improved, brighter xenon-filled incandescent bulb to replace the stock krypton bulb (for all D lights), but it doesn't extend battery life.
You can even add Malkoff's crenellated bezel and pointed tailcap to give it more striking capabilities. The problem with Maglites is that they don't make LED lamps for their 5 and 6 D flashlights yet, but at least they make LED versions of the smaller lights. A good compromise is the 4D LED Maglite, good light output and battery life. Maglite sells mounting clamps for their D flashlights, as well as belt holster loops.