well if you were to try to make a perpetual motion device, i think magnets and water are the way to go. for example, you could have ramp shaped like U but not with the vertical parts, have a metal ball rolling from the left side to the right side, in time with a magnet swinging from a wire on the right side which will attract the ball, and will make the magnet come towards the ball each time it swings, meaning, if you get your timing right, you can have a magnet that swings and a ball that rolls.
if you get what i mean. that was just an example and i didn't really think about it, it also just used magnets, but ok.