I just bought one of these LED penlights after reading a review online. It's fabulous. And very tiny, about the size of your little finger.
It takes one AAA battery and has three light levels. The lowest light level is just enough to read by. The highest lights up my whole backyard, amazing for its tiny size. They claim 115 hours battery life on low. Much less on high.
I use it outside at night when DXing to check identify radio buttons and read DX lists.
Best penlight I've ever owned. And LED too. No bulbs to go bad. All aluminum and very well made.