I like my Klarus Mi10, I load it with a lithium ion AAA, and it pumps out up to 80 lumens for a long time...works great on my key chain.
I also use an Xtar Meteor with a single IMR123, which pumps out 500 lumens on max and is built like a tank. It has both a magnetic base which is nice as a task light (clipped to the underside of the hood, you can look around under there very easily, etc...its a floody beam), and a chain with clip...which I attach to a belt loop and tuck the light into my back pocket. When needed, I simply grab the belt loop clip, and pull out the light...works well for me. Its also a great tailstand light, as with 500 lumens, a ceiling bounce lights the entire room up.
:D