My favorite thing about this movie
It's so hard to choose, but I guess I have to go thematic and say it is the absolute ambiguity the film leaves you at the end. There is no answer to the question: was he a crazy man who thought he was a vampire, or was he a vampire who thought he was a crazy man?
(I realize some people feel they have found an answer to the question, to which I salute them for that, but for me, having seen the film a number of times, I have to say, there is no answer. And I like that.)