What CelticCross said verbatim except I think he meant "micro usb" instead of mini.
To answer the question directly, my personal favorite USB rechargeable light is my mh20gt. Coupled with a decent battery, the mh20gt is a difficult stock light to beat, considering size, functionality, and performance.
Only downside is that they do not offer an nw version of that's what you are into.
Just my opinions solely based on what I own.