Well… I don’t really have fish I would never keep as I’ve kept most of the overrated ones and ones I just downright hate (such as Yellow tangs). I’ve also kept fish I said I wouldn’t keep due to difficulty. I also have some I have always wanted to keep (such as an Achilles Tang - this is one I was going to pull the trigger on early in 2022).
One fish I never thought I’d keep was this girl, my juvenile Regal Angel.
Blacktip Reef Shark (Carcharhinus melanoterus), too active and big for even the largest home aquariums, I had mine for almost 6 years, to stressful to keep it healthy!