IMHO, the best light for getting you noticed during the day is the Dinotte daytime running light. The amber color really stands out, even on a sunny day. Expensive, yes. But if you ride in busy areas where there is a high likleyhood of someone pulling a left turn in front of you, or pulling out of a driveway/side street in front of you, very worth the money you spend.

http://store.dinottelighting.com/sha...t=products.asp