I was recently hit by a car in an intersection. I suffered no bodily injury and the driver paid for a new front wheel. The incident got me thinking though. It was night and I thought I had a pretty decent front light (LED 1W?) but the driver didn't see me. I decided to invest in a brighter light. I got me an Aurora AK-P7-3 5-mode, Li-Ion cells and charger from dealextreme.com.
I also ordered a TwoFish look-alike handle bar mount, but canceled since I'm so satisfied with my current solution; I have attached a spring clamp to the flashlight. It works great and I thought I ought to share. I used a couple of zip ties for holding the clamp and flashlight together. The clamp I chose was slightly oversized so I cut strips from an old bike tire to put in the gap. The rubber also helps increasing the friction with the handle bar. Luckily the Aurora and the spring clamp both have flat surfaces engaged so they won't wobble. If you're less lucky you could put a layer of hot glue in between. If I had to do it again, I would be more careful to balance the flashlight and clamp above the bar. My setup is somewhat heavy towards the head.
+ Cheap, around 2 USD (excluding zip ties)
+ Simple to DIY
+ Very sturdy, might hold even in a crash
+ Quick one-handed mount and release
+ Possible to quickly dip the headlight by tilting
+ Easy to move from one bike to another
+ Fits a wide range of handle bar diameters
- Bulky (metal clips are smaller but might scratch)
- Mount is permanently attached to flashlight
- No sideways adjustment
- Ugly, suspicious look