I'm still happy with my Nitecore D10. It's a single AA, so pretty small, with variable brightness. On 2 lumens (just enough to read) it lasts over 50 hours on one Eneloop, and on 120 lumens it lasts around 1 hour. It uses alkaline, lithium or NiMH. The piston switch can be used as a twisty, or momentary on, or click-on. It's water-proof and very versatile as an every-day carry light.

If I were buying today I'd consider the Preon 2, which is a 2xAAA light, long and thin.

http://www.4sevens.com/