219 miles per hour (353 kilometers per hour): Bugatti Veyron
The Bugatti Veyron is the king of the beasts, as far as exotic cars go. It tops most of the lists out there, from most expensive to most exclusive to most horsepower to most coveted. But it doesn't top this list.
It is included on this list as a proud representative of all the questionable amateur videos on the Internet showing people doing dangerous things in powerful cars. For instance, in this 2011 video you can see flashing lights on the right side of the screen. There are two explanations for this in the comment-verse: either the police are chasing him (doubtful) or he has a police motorcycle escort (more doubtful; what motorcycle could keep up with him?) or he affixed flashing lights to convince other drivers to move over out of his way (pretty likely). And is he really holding his own camera while he drives?
In any case, the speedometer reads 353 kilometers per hour, which is 219 miles per hour. That's believable for a Bugatti, since they've set records above 250 miles an hour on the track. But it's a classic case of "don't try this at home" -- not that many of us have a Veyron sitting around waiting for us to do ridiculous things at high speeds.