It is almost certainly the most-heard scream in the history of the world, a high-pitched yelp of pain or terror that has appeared in dozens of films and TV shows over the past half-century. First used in 1951s Distant Drums to convey the existential disappointment of a man being eaten by an alligator, it was dubbed the "Wilhelm scream," after the character of Private Wilhelm, who uttered it after being shot in the leg by an arrow in 1953's The Charge at Feather River. Used sporadically in the subsequent decades, it truly took off after sound designer Ben Burtt used it in the first Star Wars picture.
It's appeared in well over a hundred films since then, including all the subsequent Star Wars pictures, every Indiana Jones movie, the last two Lord of the Rings films, Titanic, Toy Story, Kill Bill (at least twice), Spider-man, Ratatouille, and many, many others. The original scream is believed to have been recorded by Sheb Wooley, the singular talent who gave us the 1958 song "Purple People Eater."