Seriously though, SK68. Very good boost driver, your choice single or 3-mode, around $6-$7 shipped.
You even get these salvaged extras that comes with it:
XR-E emitter Q3-Q5
Aspheric lens
AA host body
Aluminium pill (some not hollow, very good thermal)
Multiple sized O-rings
Rubber boot
Clicky switch
Pocket clip
Crap. Sorry to hear that; I have one hooked up to a Nichia and it seems alright so far. Maybe the driver is not robust enough for drawing 3 amps. I’ll tell ya that I haven’t tested current to the LED, but it’s fairly bright. I think 2xNiMH would be more efficient but I’d be pissed if it fried the thing.
I have a single mode SK68 boost driver and it’s pretty good. I don’t know how good regulation is, but the driver is fairly flexible with different cell setups. Also, I think it has some kind of overheating warning because it blinked every few seconds when I tested it in open air off 1x18650.