A recent Slashdot thread tells the story of a famous sound effect, a particularly ghastly scream known as "The Wilhelm". In an amusing two year old radio segment plenty of samples of the use of the scream is given, and it's origin as a sound effect titled "Man being eaten by alligator". The scream has been the last sound emitted by numerous film villains, and then there are some high camp samples of sound editors working the scream into a film, like the appearance in a silent moment of a Judy Garland song in "A Star is Born". Apparantly the sound has become sort of a sound editors gag - a sound that editors try to work into projects like some kind of auditive graffiti.