9. Pulp Fiction - Magic Bullet Holes
Here's a tip: if you know you're about to shoot a scene that requires environmental changes as integral to the plot as these bullet holes, which convince Jules to give up his work as a hit-man to go and find himself, you should probably make sure they don't appear before the scene that's supposed to cause them.
Though Quentin Tarantino is a notorious film junkie, he couldn't stop this infamous gaff that showed off the bullet holes before any gun was fired, and clearly hoped that no-one would notice the whacking great holes in the wall behind Jules and Vincent. We did.
It's also not hard to see why Jules was so shocked not to be dead, considering three of said bullet holes are clearly visible behind his body, at impossible points of impact due to where the hitman is standing.
Perhaps he actually is protected by God...