The Bugatti Veyron 16.4 is among the fastest and most exclusive cars in the world. Not only do you need approximately $1.7 million to buy one, you’ll also need one very special key if you want to unlock this 1001-bhp supercar’s top speed of more than 250 miles per hour. An owner must fit the (unimaginatively named) “top speed key” before attempting to reach the Veyron’s outer limits. Give it a twist, and the Veyron’s suspension and rear spoiler are lowered for better wind-cheating aerodynamics. The steering input is also limited—at 250 mph, you want to make sure all your steering corrections are minor….