The real question should be: "which hats do you want to see?"...
Trad: just go for it and start thinking about something SharePoint-themed ^_^'.
Some suggestion (updated as new hats come to mind):
Clippy Hat: 10 answers that where flagged as "this post does not really answer the question" (OOKK, just joking here).
Voodoo Mask (has some Office simbols hanging): something similar to the necromancer badge - have to think about it.
Say SharePoint and Enter (A Moria-like gate with the SharePoint logo): ten answers about claims, form auth and so on.
Kitchen Timer (A tomato-shaped kitchen timer): 10 answers on questions tagged as "timer job".
Living Fossil (Nautilus shaped): Asked a question / posted an answer to a question tagged 2003.
Santa Little Helper (Elf-like hat and ears): one flag was deemed usefull.
Santa Claus (need to say?): manually awarded a bounty on the 25 of december.
Robot Santa (based on the Futurama char.): deleted a bounty-pending question. OR voted to delete/close X bad question/answer.
I love Version Tags (Jeff avatar hairs - Coding Horror logo): removed at last 20 useless version tags. See here.
Dromedary (a dromedary head): answered 10 questions tagged CAML (for the ones that don't get the joke... here)
Legendary Super User (Yellow, sparking, pointy hairs): reputation level is over nine thousand...
Evil Mastermind (Mandark styled): have asked a question titled "How to corrupt content database?". Why should it use that graphic? Search the question and you will understand :P (hope @Shoban doesn't get mad for this ^_^ - always loved that question, and actually tried to find some creative answer)
We are the robots (Cardboard Robot styled, with Conchords logo): triggered the Captcha check (and let's hope that the check is the same as Stack...).
April fool special guests:
Weaponizzed Pony (Unicorn Head): entered the code while on the meta site. Can add some cornify bonus for added effect.
[Title] Princess (Pink unicorn head with crown, wings and glittering effect): secret hat - requirement unknown. Must perform some specific actions while wearing the Weaponizzed Pony hat. Note that the title is random and changes beetween words like "Cute", "Glittering", "Nice" and so on...