Both, dogs and cats.
I've got a 14 year old Bichon, got him when he was 3 months old. The breeder was going to euthanise him because he wasn't show quality (he has an overbite). He's just a pet not a breeder, but the most loving and obedient dog you could want. Also a 10 year old Miniature Pinscher we got 2 years ago from a family whose son developed allergies. Then there's Salem, the Cat From Hades. Her mom was a stray who had a litter in someone's garage. Racoons killed the other kittens when they were 5 weeks old and fatally injured the mom, so we got Salem, the sole survivor. She feels she needs to defend herself from everything, not at all cuddly. But she's well behaved otherwise, and after 3 years of patience, she's finally asking to be petted once in a while. I think she might soon start to trust us.