The Wilhelm scream - most successful Sound Effect Ever.

The Wilhelm scream is a film and television stock sound effect that has been used in more than 200 movies, beginning in 1951 for the film Distant Drums.^[1] The scream is often used when someone is shot, falls from a great height, or is thrown from an explosion.

Most likely voiced by actor and singer Sheb Wooley, the sound is named after Private Wilhelm, a character in The Charge at Feather River, a 1953 western in which the character is shot with an arrow. This was its first use from the Warner Bros. stock sound library, although The Charge at Feather River is believed to have been the third movie to use the effect.^[2]

The effect gained new popularity (its use often becoming an in-joke) after it was used in Star Wars, the Indiana Jones series, Disney cartoons and many other blockbuster films as well as television programs and video games.

[source: http://en.wikipedia.org/wiki/Wilhelm_scream]