At the risk of sounding really anal, the one thing which really gets to me is old steam railway films on You Tube, where the sound is dubbed in.
I know enough about steam locomotives to know what sound a two cylinder, three cylinder, and four cylinder should make, and it's very easy to watch the wheel revolutions. Obviously a two cylinder locomotive has four exhaust beats per revolution in synch with the wheels. Much of the time this is way out, and it grinds my gears every time.
