This could be a fun topic. There is a whole subset of Hot Wheels One-and-Done models throughout it’s 50 years. Try and think of a few. I did, and made some of the recent licensed O-&-D’s my Saturday Showcase:
I have already been reminded of one in my collection that I forgot, the ’77 Mustang. Drat. There could very well be others. There are surely a ton that aren’t in my collection.
I included those that had a recolor in the same series, same year, as long as they were not released any other time. Obviously an arguable point, but it is interesting to see the many cool models that only had one moment in the sun.