I really don't have anything terribly rare, because I've only been really collecting MAC for a couple of months now. Crazy, I know. I have a Northern Lights MSF coming soon, and I got two each of Hollywood Nights and Style Minx which sold out EVERYWHERE almost. I also have Pagan e/s, Jewelmarine Glitter, Aire-de-Blu and Helium pigments...nothing terribly rare.
Edit: Well I now have gotten Angelcake shadow, the holiday 2004 Sak's Face Dazzle palette (with Swarovski), and Marigold glitter.