This video made me laugh. It highlights over 50 years of the Wilhelm Scream used in films.
The Wilhelm scream is a film and television stock sound effect first used in 1951. The effect gained new popularity (its use often becoming an in-joke) after it was used in Star Wars and many other blockbuster films as well as television programs and video games. The scream is often used when someone is shot, falls from a great height, or is thrown from an explosion.
You can read more information on the Wilhelm Scream here.