Some of you sissies are still shaving with sharpened shovels. But Mike Cook does it old school--as in using Stone Age technology. Watch him knap a slice of obsidian off a block and then shave his face with it.
Cook refers to obsidian as "the sharpest substance known to science." I don't know if that's true, but at the link, you can see electron micrographs of a surgical scalpel and an obsidian blade. The obsidian appears to have a sharper edge.