Whether I'm under a car, riding at night or digging around in my closet, it helps to see what I'm doing and be able to use my hands. The Blackburn Flea tries to beat the Mag-Light-in-the-mouth technique.
Pluses: The Flea is minuscule, roughly two inches long and 17 grams. But it outputs 40 Lumens from four super-bright LEDs. It includes clips for bill brims, straps for bike helmets, and a head band for... heads. The li-ion batteries shaved a bunch of weight compared to the AAs powering my old headlamp - which meant it didn't rattle around on its own when I went running or biking over potholes. The three-colour LED embedded in the power button that acts as the light's fuel gauge is handy.
Minuses: The small form factor makes it incredibly losable. I misplace the light or one of its six tiny accessories at least once a month. And the solar charger is nice, but sometimes I don't have five hours to wait for a charge. Also, a three-hour max runtime means you're probably not going to be riding through the night with it, but should be enough for most local tasks. $US40 via Blackburn.
The Flea charging using the included solar panel
The Flea charging via USB
The Flea from the side
The Flea next to a key
The Flea's USB charger