Cheaper Speed Please
While the Mercedes SLR Stirling Moss Edition and the MaRussia are fast, they will also cost you an arm and a leg, and a few more body parts. There are a few cheaper alternatives if you are mechanically inclined. Try putting a V12 in a Mazda Miata:
You could also go green and drive the world's fastest electric powered Go-Kart, though it is likely not street legal: