Ok i have solved all of your fighting i did some reseach and this is what i came up with:
corvette sledgehammer: 255 mph
bugatti eb 16 /4veyron: 252 mph
Dauer 962: 250 mph
Vector Avtech WX-3: 249 mph
koenigsegg CC: 240 mph
Tvr speed 12: 240 mph
McLarin F1: 240 mph
ferrari koenig racing evelution: 230 mph
Hennessey viper venom: 225- 230 mph
lamborghini VTTT: 223 mph
(note the person who said the tomahawk was the fastest, it is not a car it is a motorcycle but if it was it would but the fastest becasue it goes 300 mph plus)
So the person who said the sledgehammer was the fastest you are correct