will make quite a lot of light using a single NIMH AA that has been out of a charger for weeks (pushing ~ 1 volt...). It doesn't get you to 0 batteries, but it does a nice job of making light when you happen to realize you need it (without thinking about it in the interim).
http://dx.com/c/flashlights-lasers-999/led-flashlights-901/a...
will make quite a lot of light using a single NIMH AA that has been out of a charger for weeks (pushing ~ 1 volt...). It doesn't get you to 0 batteries, but it does a nice job of making light when you happen to realize you need it (without thinking about it in the interim).