I guess it depends what you want it for. If you want a pinpoint spot to map with, Nightmaster 800, without question. If you want a floodlight type torch, then as has been said the Ultrafire's are hard to beat for the money from the flea. If you want to go somewhere in the middle get a Tiablo A9, and buy the aspherical lens head for a focussed beam when you need it.
I shoot with a NM800 on my rifle, and I have a Tiablo A9 in my map pocket for searching out closer areas/finding bodies/ checking we're not about to drive in a bog...!! The Tiablo has a half and full power on it too, which is useful if you're trying not to blow your night vision. The NM800 has a H,M,L setting on the white LED only.