Although not purely American, the 427 Cobra is one of the best-known muscle cars ever made. Based on a lightweight British AC Ace roadster, the Cobra was the brainchild of automotive legend Carroll Shelby, and it was essentially created by shoehorning a mammoth Ford 427 engine under the AC's hood. The end result was a frighteningly fast roadster that was also tremendously successful on the track. Today, top examples of these cars command incredible figures at auction houses worldwide.