Wall mounted ball run. This would be great for kids who are too young for the marble runs. Could be used as a music installation if there are movable obstructions in the pipe that make sound when a ball touches them
DIY HOME Candle Powered Heater - I've been looking a various ways to make these and this guy has by far the best setup. It isn't so much a how-to video. He is just showing what he used to construct his version of the terra cotta pot candle heater.