I didn't get to drive it, but Mark Heffington (owner of Hypertech) gave me a ride in his Lingenfelter twin turbo C5 Corvette years ago. That thing was just stupidly fast - and from the passenger seat it only feels moreso. At the time I compared it to the downslope of a rollercoaster but straight forward, that same gut-in-your-throat feeling. Totally awesome.
oh hey I think that's it in the foreground
http://www.hypertech-inc.com/Mark.aspx
Fastest I've ever driven is my cammed '99 Trans Am. I miss that car. Was working for Comp Cams at the time and just about exhausted their catalog on that thing.