T-800 rips its skin off

John hands the T-800 a knife and orders it to show Miles Dyson what it really is. The T-800 slices through the organic covering on its left forearm, then peels the lot away to expose the endoskeleton arm underneath. It looks impassively at the limb, a few shreds of bloody flesh clinging to the metal, and flexes the joints a bit. Miles and his wife are horrified by the revelation. (Thankfully, John had the good sense to take their son out of the room before the T-800 began cutting.) It takes Miles a few seconds to fully understand what he's seeing...and then he's horrified for a different reason. His wife meanwhile (probably) didn't recognize the significance of the arm, but was nonetheless freaking out over the sight of a man ripping off his own skin and muscle.

Example of:
Self-Mutilation Demonstration