Trustfire 3T6. Because it was £30 including a set of 18650s, charger and postage - effectively a "starter kit" for high-powered lithium torches.
Have to keep an eye on battery voltages as the included 18650s are the dreaded blue Ultrafires, with no protective circuit, and the charger is the standard "dumb" item that gives an open-circuit voltage of 4.26V (on a calibrated Fluke 289) - i.e. has potential to slightly overcharge the battery.
But it all seems to work well and the 3T6 is phenomenally powerful for such a cheap and relatively compact torch!