I have a small Romisen CRE LED light powered by one AA. It fits in a pocket and it's as (or more) powerful than my big 6V lantern battery powered light that weights like 2-3 lbs. I took it along when camping and in pitch black night I can literally see several hundred feet ahead. Amazing. I use it with regular alkaline batteries as carrying a charger is not always practical.

I also have a couple of other CRE flashlights, including 2AA Terralux and small Fenix but this one has the best power to weight/size ratio.