I was pleased to learn that I could get a replacement "bulb" (more of a bare chip mounted on a bulb base, really) for my old-school Maglite -- the type that takes multiple D batteries, has a focusable beam, and will serve as an improvised bludgeon if need be (because it's made of honest metal).

While I haven't made any formal measurements, the result is several times brighter than the old bulb, and of course the batteries last many, many times longer. Recommended.