My band saw. I didn't do anything wrong (I swear!). I hadn't used in it many years, and when I turned it on it made a horrible broken/about-to-explode noise. I checked inside, after turning it off, of course, and the rubber "tires" that go around the pulleys were dry, hard, brittle and cracked. The blade had come off the pulleys, that was the scary noise. You don't want power tools making noises like that, trust me.