What anime are most representative of the medium?

A friend of mine recently asked me what anime is. Adhering to the show-don’t-tell school of thought, I am trying to find some titles that convey the overall feel of the medium. I am looking for an honest snapshot, so favorites and best examples aren’t necessarily going to be helpful.
I realize that no single show is going to do the trick, but I’d like to keep the list shorter than “All of them.”