The Nitecore TUBE keychain light puts out 45 lumens of quality white light from a tiny package. They come with 2 variable brightness settings and a maximum runtime of 48 continuous hours. Rechargeable with any micro USB, these are the smallest rechargeable lights on the market! And from a company like Nitecore, you are getting a high quality product!
Manufacturer specs:
http://flashlight.nitecore.com/product/tube