Revealing mistake: The scene right after Mrs. Moore delivers the first batch of telegrams shows Lt. Col. Moore kneeling beside several "dead" soldiers. I could see at least the first four breathing.
Revealing mistake: On the battlefield where Mel Gibson first talks to the reporter, there are bodies of dead men lined up on the ground. You can clearly see one of the dead men breathing.
Revealing mistake: Snake Shit's helicopter has no holes in its windshield. Every other part of the helicopter is riddled with bullet holes except his perfect, spotless windshield.
Revealing mistake: Towards the end of the movie, a VC soldier holds a shoulder fired rocket launcher. If you watch carefully, you can see the rocket wobbling as if it's made of rubber.
Chosen answer: Smedley Butler and Daniel Daly. Both were awarded the medal of honor twice, and lived to tell about it. Both were also U.S. Marines. More info here at http://www.grunts.net/legends/butler.html and http://www.cmohs.org/recipients/double.htm.