A flashlight has housing with a first mechanical spiral engagement system, a head assembly with a second mechanical spiral engagement system that engages the first mechanical spiral engagement system when the head assembly is coupled to the housing, an LED light source module fixedly held by a heat sink fixedly held by the housing, a power source held within the housing, and a switch assembly, wherein light provided by the LED light source module may be varied by rotating the head assembly relative to the housing while the heat sink, the switch assembly and the power source remain stationary.