well the spirit of america is sure fast. but technically it is no longer considered a car. it close to being a jet aircraft, just add wings though. so is the british "car" owned by richard noble. geez, i can't even recall the name of that black, twin-engined "car".
anyway for european cars, there are bugatti, koenigsegg, ferrari, benz' clk gtr, and so on. but one of the fastest is the porsche carrera gt. for americans, there is the historic chevy corvette, ford mustang, shelby cobra, dodge viper, and so much more muscle cars. for asian, there's nissan skyline gt-r, mitsu EVO series, mazda rx-7, honda nsx, toyota celica, and endless others.
but for me the fastest car, and technically a car, is the one sans fenders. you got it. an F1. be it ferrari or whatever...