I use a Fenix L1T. It has a 3W white LED and works on a single AA cell. It will work well on rechargeables too. The flashlight will operate on very low battery voltage. I used cells that were detected as empty by my GPS unit with good results. Rechargeables should not be used until the light goes out. That could damage the cell because of the low voltage.
I like the flashlight because it is very compact and lightweight. It produces a pretty bright beam. The switch is protected against accidental operation.