Considered the fastest sedan in the world, the Brabus Rocket (Mercedes-Benz CLS V12) is from the Tuner GP in Hockenheim, Germany. Some people don't even consider this a Mercedes-Benz CLS anymore because it is so heavily modified by Brabus. It is also referred to as the "Brabus CLS V12 S Rocket." You can view pictures at: Brabus Rocket – Wikimedia Commons and a police car version at automotive news. Here's a YouTube video (in German) for those interested:
http://www.youtube.com/watch?v=LShZ9_Rzbqs