2012 Mosler RaptorGTR, #1 of 1, on sale for $700k
You hear the term "one of one" a lot in the classic car realm. It is meant to indicate the utmost rarity in a vehicle with an extremely limited production run. In contemporary cars, other notable examples include a one-off Bugatti Veyron, or the Ferrari P4/5 commissioned by James Glickenhaus.