I've had some heartbreakers.
SAFN Egyptian contract w/ spare barrel. I put it up for sale at three bills when I was in dire need of cash. The buyer was literally leaving with it when I went in to pull it off the line.
Colt Police Positive Special. Second Gen. A somewhat ratty old piece I could never justify having. I bought and sold it several times over the years until I lost track of it.
CZ 452 .22. Shot hundreds of small game animals with it. Absolute tack driver. I bought it in 2000 when they were still dirt cheap and before there was a CZ-USA set up or the "A" (America) prefix rifles out. Lost it in a separation, but the good news is I reclaimed it after buying the ex a new CZ. It was all rusty, but cleaned up nice. I'll never let it go now.
Mosin-Nagant M-39 from my birth year. I stupidly let it go because I was out of room. I want to get one again some day.