A self-contained, rechargeable LED flashlight uses a zener diode in reverse-breakdown avalanche mode as a low-cost voltage regulator. A second embodiment of the LED flashlight incorporates boost-buck circuitry to allow the internal rechargeable flashlight battery to be recharged through external dry cells. An LED or LED array of the flashlight may be by passed with operator control to allow an internal battery to operate an external device, such as a cellular telephone or the like.