Yesterday evening I watched Akira Kurosawa's The Hidden Fortress.
This was one of those movies that are perennially cited as one of George Lucas' main influences when conceiving Star Wars.
In fact, as one of the extra features on the DVD there was a short interview with Lucas, in which he discusses how much he admires Kurosawa's direction and vision, particularly in comparison to other movies at the time. For a movie this old, I was very impressed. I have some other favourites from the fifties (On the Waterfront, Twelve Angry Men), so I am not dissing all films of this era, but this film really stood out as something very impressive for me.
In case you are wondering, the influence that is most obvious in Star Wars is the use of the "two lowliest characters" to tell the story. The two peasants in Kurosawa's film are evidently C3P0 and R2D2 in Lucas's epic.