The Ultimate GTI in every way -- VW Golf GTI W12 650

There's fast and then there's uber fast. The 200hp Volkswagen GTI is pretty peppy in its own right, but the German carmaker was far from satisfied. Thus, they created the Golf GTI W12 650 concept vehicle at Worthersee 2007 in Austria. They're saying that this is "the ultimate GTI in every way", with its 0-62mph time of just 3.7 seconds.

Keep the pedal to the metal and this rabbit on steroids will keep going and going until it tops out at around 325 km/h (201mph).
They don't plan on selling through their dealerships -- it's "a pure show car" -- but it surely shows what the company is capable of. I guess having both Lamborghini and Porsche backing you up goes a long way, because this pocket rocket produces 650 horsepower (hence its namesake) and over 530 lbs-ft of torque. This is thanks to the monster 6.0L biturbo W12 it's got mounted behind the front seats. It's also 100% rear-wheel-drive.
But it's not just the engine that's different. It's lower and wider than the stock GTI, it's got a bunch of new intakes and a redesigned C-pillar, and they've designed the carbon fiber roof so that it can act "as a giant diffuser that funnels air under the smaller spoiler at its trailing edge." This was so that they could avoid the installation of a massive wing out the back.