Ground-Bond Testing

We're all familiar with the "three-prong plug" on some electrical equipment. The third prong which, on North American standard 120VAC plugs, is either cylindrical or U-shaped, connects part of the electrical device to ground.

Is the third prong optional? 

NO, not really. If the device was equipped with a grounding, 3-prong plug at the factory then it is an absolute requirement.

But you have certainly seen electrical devices with just a 2-prong plug.