Sci-fi must-reads?

Well, list some and I'll read away like a constipated god.

P.S.
I read Dan Brown, so feel free to suggest intellectuel books.

>>26
Cyberiad ftw.

Good suggestions in here.  I'll add a couple.

Light reading:
  Neal Stephenson - Snow Crash
  Neal Stephenson - The Diamond Age
  William Gibson  - Neuromancer (and direct sequals)

Heavy reading:
  Samuel Delaney - Dhalgren
  Robert Shea and Robert Anton Wilson - The Illuminatus! Trilogy