"Jason and the Argonauts" (1963)
First saw this classic fantasy film during my childhood, and ended up being absolutely terrified of those morphing skeleton warriors - had nightmares for days as I recall!
Never tire of repeat viewings, especially the brilliant stop-motion special effects by the SFX God himself, Ray Harryhausen!
The story is fairly routine, but the film lives off the battle-scenes, and the mythical gods such as Talos, and the hydra amongst others. But it will always be those creepy, gaunt, "smiling" skeletons that most people will remember: which is an awesome feat for a 54 year old film competing in a contemporary era of unmemorable CGI!
*Interesting footnote - Todd Armstrong (who played "Jason"), only got the leading part because of his looks rather than acting ability. Moreover, the studio couldn't afford big stars due to a lot of the budget being allocated to Harryhuasen's time-consuming special effects. Armstrong would later commit suicide (1992) due to painkiller-addiction.
Classic stuff , Its too bad they don't make films like that anymore.