Factual error: In the scene where Wolverine is shot in the head the bullet stays in place until it falls off. Wolverine's skull is indestructible Adamantium (that doesn't even bend slightly from the impact), and an object that applies a certain amount of energy towards another object has the same energy applied to it in return. Considering the bullet's high speed (which means high energy) and the fact that there is not enough material around Wolverine's skull to absorb the bullet's energy, the bullet should have bounced right out.