TITLE: What are the most important results (and papers) in complexity theory that every one should know?
QUESTION [13 upvotes]: A few years ago Lance Fortnow listed his favorite theorems in complexity theory:
(1965-1974)
(1975-1984)
(1985-1994)
(1995-2004)
But he restricted himself (check the third one) and his last post is now 6 years old. An updated and more comprehensive list can be helpful.

What are the most important results (and papers) in complexity theory that every one should know? What are your favorites?

REPLY [4 votes]: There's the Bazzi/Razborov/Braverman sequence on fooling AC0 circuits.