The story of this car is the story of America, in that it did what we do best: make the Brits look like idiots. In 1962, Texas chicken farmer Carroll Shelby took the diminutive British AC sports car and shoehorned in a series of robust Ford V-8s. First came the 260-cubic-inch 8-cylinder, followed by a 289 cubic-inch version, but those proved too sensible. The 1965 427-cubic-inch V-8 (that's 7.0 liters) put an exclamation point on Shelby's ingenuity. The 427 is why nobody drawing breath knows what AC is and why Carroll Shelby is a living Jeopardy! question.
The 427 didn't handle any better than the 289, but it was a lot more powerful, and it showed. Its basic shape dated back to the '40s and was derived from the foundational Ferrari 166MM Barchetta, or "little boat." But with a gaping mouth meant for gulping great quantities of air, fire-belching side pipes, and huge rear fenders that announced where all that power originated, the Shelby transcended mere sports car-ness to become America's first supercar, an unqualified legend. The hotness in the collector-car market nowadays might be in late-'60s American muscle, but the Cobra is the foundation for that subspecies of Yank Tank. And when the muscle-car bubble bursts, the Cobra will keep appreciating.
What to watch out for: There have been so many Cobra replicas (some even built by Shelby himself) that the most important consideration here is authenticity. Be sure yours has proper documentation and the correct serial number.
Resources: Shelby Cobra: The Shelby American Original Color Archives 1963–1965, by Dave Friedman; Shelby American Automobile Club; The Cobra Story, by Carroll Shelby