These are the rarest cars I saw at San Francisco Sports Cars in San Carlos, CA.
Ferrari 456M Schumacher Edition, 1/less than 20 worldwide, like 3 in the USA. This is actually the only 456 I've ever gotten a picture of.
Koenigsegg CCX, 1/14 worldwide
Dodge Viper SRT10 Roadster Final Edition, 1/18 worldwide
Superformance 20th Anniversary MKIII, 1/20
Ford Mustang Shelby GT500 SCJ, 1/145
Maserati GranSport MC Victory, 1/180
Ferrari F512 M, 1/500