Serfas Thunderbolt

I have two of them. They mount on different parts of the rack on my main commute bike, or on the rear triangle of my mountain bike; the straps make it easy to locate them almost anywhere. Each one is brighter than my Radbot 1000 and the boyfriend's Planet Bike Superflash combined. I like that they can be recharged instead of having to use batteries. The only downside is that the runtime is fairly short, so I have to recharge every other day or so.