Lezyne Mega Drive or deca drive:

http://www.lezyne.com/products/led-l...ce#!mega-drive
http://www.amazon.com/Lezyne-Drive-L...yne+mega+drive

I have the mega-drive for not very long now. I have rode home in complete dark, which includes unlit trails, through woods, and street 3 times now and am really liking it. It can do 1200 lumen but the 600 setting is more than enough. It is also very well designed and crafted and looks to be solid waterproof (the USB charging port is inside the sealed case -really nice seals - you open the sealed back to access the port), and you can use spare batteries.

Here is a review:

http://reviews.mtbr.com/lezyne-mega-...ights-shootout

I bought a Belkin 2.1A USB charger for $10 off of Amazon and it charges in about 5 hours. And unlike other brands, it really does deliver the lumens it says it will.