Listed in Middletown, MD – just outside of Frederick near the Pennsylvania state line – this (presumably home-made) kart packs a small Boeing gas turbine engine and said to be good for over 300 pounds of thrust. And from the looks of things, it does not appear to be driving through the wheels, so it's a purely thrust-driven affair. It also has a frame, a seat, steering wheel, four wheels, some little disc brakes, and... that's about it.
In short, it could be the perfect gift for the person you love most, or least. Whoever it's for, and whatever the reason, it's not cheap. The seller is asking $10,500 for the wild creation.