Non veni pacem mittere, sed gladium.
I happened upon these little wonders several years ago, and have made gifts of them to just about everyone I know. Recipients are usually gobsmacked!They are amazingly bright, use 1 AA battery or (if you prefer) a lithium-ion. The battery lasts for ages, with occasional use. The light can be focussed or diffused; they are water resistant (but probably not fully waterproof, I wouldn't recommend them for diving.) Highly recommended!
I purchased 5 of them. Put the Lithium batteries (Eveready Energizer Ultimate 9x) in them. They keep working, time after time. Impressive! Quite bright too. The best deal going!