Ay Up road lights for me. Not cheap. I think I paid about £190 in 2010 and purchased them on the advice of the ever knowledgable Audax community in Scotland.
I have used these lights for commuting (11 miles each way on very rural roads) on a daily basis both as lights to be seen by and lights to see by. They have performed flawlessly, they are robust, totally waterproof and spare parts are readily available from the vendor. I have recently acquired an uprated battery for longer distance Audax rides.
While the up front cost is considerable I consider these lights to be an long investment.
Usual caveat: No connection with the company, just a happy customer.