SR-71 Speed
Brian Shul has a great story about requesting GS from ATC in his Sled Driver book. Basically, there's a strong tail wind and requests for GS start from a Cessna, one-upmanship begins with a corporate, then a military fighter, then finally Shul's backseater requests GS for "Aspen 20". Long pause from the controller, uuuuum Aspen 20, I show 1700 knots GS. There were no other GS requests that day.