For many applications a 1 watt LED in a 2+ D cell light is more than adequate. If you have an old MagliteŽ Flashlight which takes between 2 & 6 D cell batteries you can do a lot worse than upgrading with a 1 watt Terralux Ministar LED. For $12.95 you turn a crummy light into a pretty darn good LED flashlight with a lot of throw. The 2 D maglite in my truck has one. Not as bright as the 3 watt in my 3 D Mag, but the runtime should be longer.

Edit: According to the review it doesn't need to be a Maglight. Lots of old D cell lights out there. Dunno, I've only upgraded my Maglites.