My vote would be for Jerry MacNeish’s '67 Z/28. Maybe not the rarest of the rare, but still pretty darn rare. It also has a great story to go along with it. It's been a while since I read it but I think the story mentions that it was cut up and run as a Super Gas gas (the horror!) and then brought back to it's original glory.
http://z28camaro.com/wp/lzp1/