Harry Potter and the Chamber of Secrets
During the scene where Harry and Draco are dueling, you can see a cameraman clearly in the shot. Because the colors all blend together, it happens so fast that if you blink, you really do miss it. Unfortunately, it's the sort of mistake that can't be edited out in post.
Captain America: The Winter Soldier
The passage on Nick Fury’s tombstone quotes a passage from Ezekial 25:17, which is also a famous speech from Samuel L. Jackson’s other role in Pulp Fiction. Sometimes directors place these actor-specific Easter eggs in films just so die-hard fans have something to celebrate. This one was extra clever.