I have a Lupine Edison 10. Save your money, though--they cost a bundle.
It's the brightest thing out there. I'm visually impaired, but the Lupine doesn't seem to know that.
http://www.singletrackworld.com/article.php?sid=1130
http://www.offroadadventures-online.com/equip044.html
http://www.lupine.de/en/home/index.html