I love the "Petzl Tactikka plus". It has a flip-down red filter, nice for preserving your night vision when flying. Even my wife likes it for reading in the tent. If you don't need the red filter, the version without it is called the "Tikka plus". There's another version called a "ziptikka", which has a retractable headband so it packs a lot smaller. All of them use 3 AAA batteries.

If you really want small, I just got the new Pezl e+lite. But it uses 2 CR2032's, which cost a lot more and probably have a lot shorter battery life. I like it so far, but it hasn't run out of the first batteries yet.