Thankfully, I haven't had any of those yet. I haven't really gotten sold/traded an number of animals yet, I waffle a lot and go back and forth on "should I" or "shouldn't I" on removing animals from my collection.
I did give away a male I produced. He had cute little nose dots and some unusual "moustaching" around his lips. Adorable.
I gave him to young man (what DO you call a 13-14 year old boy these days anyway?!?!?) who had a bad experience with a BP. His friend didn't want his any more so he went out and spent the money to get all the enclosure set up. The snake died within 10 days, apparently his friend had lost interest and just quit feeding the poor thing. It was emaciated.
It felt pretty good when I ran into him again a few weeks later and asked how the snake I gave him was doing. He called it a "beast" and it had a better feeding response than his corn snakes. That made me feel pretty rockstar.
There are a few I came VERY close to removing from my collection and am VERY thankful now that I did not.