I seriously thought about going as Joker, but then I looked up the make up kit and other clothing/supplies on ebay and I realized I'm not going to spend that much money on a costume that many people will have. If it was original, I would spend the money, just like when I wore this:
http://www.collegehumor.com/picture:1783345
I think this year I will go simple and be 1/2 of the Laser Cats duo.