Ask the readers: the most hackish Facebook applications?

I’ve never been much of a Facebook application user, but I’ve got a backlog of requests from friends who use them… Scrabulous, IQ tests, vampires, etc. I poked around the Facebook application directory and I can sort by popular, active, and newest applications, but I got to wondering about the kinds of applications that would interest Hackszine readers: really neat hacks that use the platform in a freaky way, cool applications that a hacker put together in their free time, and interesting mashups that pull data from a variety of places.

Have you come across anything wild and hackish on Facebook? What can you tell me about the application and the author? What cool stuff is going on under the hood?