Harryhausen pioneered the “Dynamation” stop-motion model animation process, which changed how fantasy and SF films were produced, no longer reliant on just human interventions, real special effects had arrived and was to provide the main influence for all the CGI we see today.

For more in depth review of his work and live click here but I shall forever associate him with the skeltons in the Voyage of Sinbad and Jason and the Argonaughts.

harryhausen_skeletons

Filmography (from Wiki):