I have 3 bikes and use lights, night or day. So I have a few
that I use; Planetbike Superflash Turbo, Cygolite Hotshot but
the brightest rear light in my collection of bike specific lights is
a Xeccon set. Here it is in actual use in traffic:

http://www.youtube.com/watch?v=_G746...6zPoymgKaIoDLA