What are some good party themes?

It is always fun coming up with a party theme. There are classic themes like 'pirate party'. Then there are edgy ones like 'Crack pipe and concrete slippers'. Interactive ones like 'rubik's cube', where you have to swap around pieces of your clothes with other people to match all the colors. Or a 'red' party where you have to wear red, and a 'white' party where you have to wear... white. A good one was a 'mix tape' party, where everyone had to bring a mix CD and swap it for one someone else made.

What are some good party themes you've heard of or made up?