I recently bought this
http://www.amazon.com/gp/product/B00KM01XEA/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1
Probably the best light I've ever bought.
Since I bought it, I've used it 10 days straight for about an hour long rides eash night and the battery is still strong. The light is...