Of course, there is no definitive answer. (Unless, you want to say the answer is 42)
However, I love the discussions, debates and memories that are brought on by recollections of those things that bind us as a geek community. A lot will come from movies, but not all...Carl Sagan, Dr David Attenborough and others have provided us with some find quotable quotes over the years...
Still for me, it is and always will be "The Princess Bride".
"Hello. My name is Inigo Montoya. You killed my father. Prepare to die."
A Little off-topic, but I once got into an argument with a friend who called him Indigo (added a D). So I corrected them and verified I was right by watching the credits. They then claimed that in book, which they've read many times (I have never read it), he is called Indigo, with the D so the director must have changed it for the movie. That's when I searched Google Books and showed them I was right, he never had a D in his name.
But as for quotes, I can't really think of any right now, that haven't already been mentioned.
Dave. I too have had that argument. It is a pleasing one to win. Not sure why. But it is.
I know, right? :-)
maybe that is another comment thread....?