I've been using bright daylight-visible flashing lights whenever I'm riding on roads. With all the distracted texting drivers, we need all the visibility we can get. These can save your life for $75.
Like other LED lights, these have been getting better rapidly.
Something like a Planet Bike Superflash Turbo used to be considered a strong light. It's been left in the dust with newer generations. It also has a very narrow beam so it's only decent if it's aligned perfectly.
The Cygolite Hotshot 80 and Bontrager Flare R are both 4x as powerful, for the same size and similar cost. They have a slighty wider beam too, so alignment isn't quite as critical.
I have the Flare R and people say it's really visible in daylight.
Niterider just released their Solas 150 which will blow them away in overlal power. Still similar size and $.
**note- later reviews are saying the Solas is more about a wider beam than more intensity**
There are some uber-powerful flashers that run on separate battery packs and can be expensive, but the Solas looks like an incredible bang for the buck this year.