I have several of Target's "River Rock" brand of headlamps that are basically the clone of the Streamlight Enduro - runs of 2xAAA batteries, has a low, high and off cycle to its levels. Adequate for many of the tasks you'd want a headlamp for (walking around in the dark, working on something within arm's reach).
I'd
like to transition to one of these:
Fenix HL20 or
Icon Irix or maybe
Icon Irix II I've begun transitioning all my flashlights over to AA or AAA, and I find that the flashlight "arms race" has reached a point where I'm ready to step off the constant quest for brighter, more powerful, and settle on "great output, great UI, common batteries."
I like that all three of these are 1xAA. The Fenix feels more solidly built. I do like the adjustable beam of the Icon headlamps, though.