Revealing mistake: During the shoot out with McGivens's gang at the Cortez ranch, the wife of Cortez sneaks out of the trap door with her baby and peers around the side of the building. You can notice that the baby is really a doll.
Revealing mistake: When Jack and Ennis are cliff diving naked, if you look closely at Jack when they both run and jump off the cliff you'll see that it's not Jake Gyllenhaal but rather his stunt double.