I sold a Colt King Cobra .357 in bright stainless with a 4" barrel that I think about often. I bought it new in the late 80s when I had my FFL, and sold it a few years later to fund another gun purchase. I don't even recall what I bought with the money, but that's the one gun I wish I still had.
Colt Combat Commander 1911 in .45 ACP. Bought it new in mid 80’s and sold it because I needed the money for something else at the time. Oddly enough I still remember the serial number off the top of my head. I should have never let that one go.
I bought a Mosin Nagant from a member here, kept if for years and loved it, it was a great shooter. I ended up swapping it for a .22 pistol since it would be cheaper to shoot. I could have kicked my own ass for doing that.
Honestly I’m a gun nut so no many I’ve sold that I want back however my M9 and German Mande 226 always come to mind of one’s id but back today if given the opportunity to do so.
S&W Model 66 .357 in stainless with 2 inch barrel. Was super accurate but had to sell when in school and have always regretted. Now have a no sell policy.