I recently purchased the niterider mini 300 plus (the plus means it comes with helmet mounting kit). I really like it so far, especially since you can keep the battery pack off your helmet. Overall, it seems well made, though as a commuter I wish that it had a quick-release mounting system; it uses a rubber band system which seems fairly sturdy, but isn't quite as quick off and on (the helmet mount is quicker, though). The biggest issue is run time; 2 hours at 300 lumens, and I believe 5 hours at 100. For a bit more you can go up a level and get some more run time.
@chefisaac. I've been using the Gemini Titan for about a year now. I had a battery issue early, but it was replaced on the spot (bought it from a LBS). Thing is crazy bright, and now that it's been discounted, it's a great deal. It mounts securely on my helmet, and a keep the battery pack in my backpack. My winter was on the west coast (think wet but not cold), so time will tell how it will handle colder temps.
Rivendell Sam Hillborne, Brompton S3L, Masi Adventure Bike (Gravel Grinder)
I know it isn't the brightest but I have the Light and Motion Vis 360. There so many features that make this light worthy of consideration. First it is light, as in doesn't weight that much. Second it has the rear light attached, plus the side amber lights. It really can be seen 360 degrees. The switch is nicely done with a softer rubber than my other Light and Motion Stella and Nite Rider MiNewt, so it is easy to turn on and off and to cycle through high low and flashing. The mounting system on the helmet is quite effective. I like the light especially mated to my Stella on the bars. It gives me plenty of light for my commute.
So far, my favorite has been my two S-Minis (one XP-G, one XM-L). Without a battery, it's about 50 grams. Heave an 18650 in there, and it's still lighter than some 1AA flashlights! ~350 lumens, available in XP-G for a more focused beam or XM-L for a more floody beam. I attach mine to my helmet with a couple of good rubber bands when the need arises.
For beam comparisons on the S-Minis, right-click each of these links, open them in new tabs, and flip back & forth: