Funnily enough (considering your example in your opening post Scott), one of the two watches I've regretted selling was in fact a Steelfish.
I picked up a first gen SOSF (the 42mm version) when it first came out a good few years ago and absolutely loved it. It was the silver dial version and it looked superb. Then Breitling released the 44mm version and I instantly wished I had that one as the added width suited the thickness a little more IMO, plus the seconds track was no longer interrupted by the date window : it just "worked" a little better all round visually. So I sold my 42mm and a little while later I picked up a black dial 44mm SOSF, which quickly became a favourite of mine. Then, for some reason unknown to man nor beast, after a few years I sold it to help fund something else. I can't even remember which watch I sold it to help fund now, but either way like a mad-man I sold my 2nd SOSF.
However, after a few months I found I really missed it, so I started looking for a 3rd SOSF. I really wanted another black dial version, but found an absolutely killer deal on a 44mm silver dial version, so I picked that one up..... but it never really hit the spot unlike the black dial version for me, so a couple of years later the 44mm silver one was history as well. I'd still like to pick up a black dial model again, but mint condition ones are harder to come by these days, so I'm not sure I will ever have another....The only other watch I regret selling is my Bentley Le Mans LE. For reason I just fell out of love with it for a period of time, so I put it up for sale and it sold incredibly quickly. As soon as it was gone I pretty much instantly regretted it. I've thought about picking up another, but they all go for silly money these days, and mine was mint so a replacement would have to in amazing condition to tempt me. That said, the lack of an in-house movement on something that expensive puts me off, so I'd love to pick up the new Bentley 24Hr instead..... but they are pretty hard to come by too for sensible money.
Omega dress watch sporting a nice leather band that was no longer in any rotation. It was offered to my nephews at a small fraction of market value - the first "I'll take it!!" got it. So now a nephew (who would not have purchased such a watch on the open market) is proudly wearing it. No regrets and no need to replace it.