I got 2 of these solely for flashing mode duties in both daylight and at night:
Rosewill RLFL-11002 3W 220 Lumen Cree LED Aluminum Flashlight w/ Bicycle Bracket

The bracket alone is worth the price of admission. The LEDs are not that great for illuminating the road ahead because of the lack of reflectors or lens but they are great as a "to be seen" light. The lights flash about 4 to 5 times a second.