Here is a few sold and regretted:
1956 Chevy 210 2 door sedan, chased for 5 years, along with several other fellow HS kids, from original owner who I think liked to tease us kids; bought from person who was successful in prying the car away only to get laid off before doing anything to the car, I did a pretty respectable restoration, got Corvette fever and swapped for a '71 roadster. Biggest automotive blunder I ever made. In over my head on that POS and did not even keep it a year. Tastes change and I am not that big of a tri-five guy these days, but I did get a good screwing on that deal.
1973 Triumph TR-6 - just a great all around car. Kept for 5 years.
1939 Chevy sedan - I was third owner of this all original, sold due to loss of storage and frustration that I was not in a position to do much with it with first house, young family, etc. This would have been an easy car to restore to a high level. Did not get back into the hobby for over a decade.
1939 Packard 120 - held for about 5 years, we moved it along a couple years back and I do miss that one.
Lost Opportunities:
1948 Pontiac sedan - Dad and I were close on this one in 1977, at a big annual swap meet in Foxboro, MA, at the old Pats Stadium, I do not think they do this one anymore. An all original
#2 , around $3K, not small change in 1977. We talk about that one to this day.
1967 Jag XKE coupe - a local car I could have had in the mid 80s for around $4,500, long term or original owner, dented "bonnet" but pretty sound otherwise. We looked at another one a couple years ago at Lime Rock, but I passed on that one due to the fact it had been a theft recovery and had a NYS issue VIN - a couple friends said resale would be tough, but it ran well, and was fairly solid. They are still very expensive to restore even to driver level - and at the end of the day the 2+2 is the least desirable.
1933 Peerless Club Sedan, CCCA Classic, about 5 years ago I could have swapped my Packard and some cash to a friend for this one of one car, but had not had it that long.
A couple of MG T cars...
There were others....