13. Baghdad Battery
The Baghdad battery is one of those wonderful objects which everyone thinks they know what it was used for, but that's not strictly true, despite Mythbusters showing that this setup could have produced an ancient charge, and used for electroplating. However, there's no contemporary evidence of electroplating in the region, and the charge produced by the battery would be absolutely minute. This isn't an ancient battery, it's way too weak. Sure, you could generate a current, but it was far too small to be of use. What's far more likely is that it was used to preserve scrollwork, but where's the fun in that?