The door from the opening of the sci-fi series The Twilight Zone comes to mind. There are so many examples to choose from. But maybe you've seen some of these more recent illustrations of the door's powerful symbolism: The use of doors in Pixar's film Monsters, Inc., the movie and tv series of Stargate, the use of doors in The Shawshank Redemption, The Room of Requirement used in Harry Potter, the changing door in the animated film Howl's Moving Castle, the use of doors in the HBO film Temple Grandin.
One of my favorite examples of the door is in the film Jurassic Park at the climax inside the dining hall. That scene where the raptor slowly opens the door that everyone thinks it's not smart enough to open! The list goes on and on! Like The Raven by Edgar Allen Poe or H.G. Wells' The Door in the Wall, which the image accompanying this post is loosely based off of.
Remember doors are also a tried and true staple of design. That door to your bedroom and every door in your house has been designed, not just to open and close, but to greet and say goodbye. How many doors take center stage in your favorite stories and images? How many in everyday life?