A famous actor died because of this, Dont recall off the top of my head who it was, but his head wasnt very solid after that incident.
Jon-Erik Hexum; f*cking around with friends on-set, put a blank-loaded revolver to his head and fatally spalled a chunk of skull into his own brain.
Brandon Lee died as the result of an inexperienced prop staffer switching out dummy rounds for blanks; one of the dummy slugs came loose, stayed in the cylinder, wasn't counted by the staffer (because she didn't bother to do the usual safety-count) and when a blank was pushed into the chamber behind the slug, the gun became a for-real deadly weapon.