As I'm winding down and selling off most of my bikes I started thinking about the one bike I wanted to build, but never will. For me it is a replica of the CZ "Rocket Rex" Staten used to holeshot the world at the 1975 Carlsbad USGP. The bike was a red-framer with the shocks moved forward (instead of cantilevered), with a Bassett pipe and motor work by Harry Klemm. I would have put Maico forks on it like Rex had before the CZ factory guys made him take them off.
For you what bike is the one that will probably never be?