BMW only built 700 of these for the entire world. It arrived with water injection technology borrowed from Formula 1, and most buyers locked them away the moment they arrived. The clock is already ticking on this one. The C7 Z06 was America's last naturally-aspirated war cry before forced induction took over the Corvette lineup for good. Built around a supercharged 6.2L LT4 pushing 650 horsepower, it was a street-legal track weapon sold at a shockingly accessible price. Collectors are only now realizing what they let slip through their fingers.