[Robbtoberfest] has earned our admiration with this crazy chainsaw powered spot light. It looks horribly dangerous, extremely inefficient, and woefully under engineered. We absolutely love it.
This could be plucked from a video game or a movie and seems to be one UV bulb away from being the ultimate post apocalyptic zombie vampire Armageddon weapon. He has taken apart a chainsaw and attached it to a DC treadmill motor using a couple of bike sprockets and a chain. That DC motor then feeds a car headlight directly. As you can see in the video, when he cranks the gas, it shines pretty brightly. The unfinished nature of this is due to a deadline for a contest on instructables, so he plans on adding a protective cowl, some fancy paint work, and a voltage regulator down the road.
While this may be inefficient, it is certainly a step up from a steam powered spud gun.