It's an odd thing, for for ages my LFS had a couple of polypterus in and I used to vaguely look in the tank and wonder why people would want to keep them. Now I'm crazy about them!
I love catfish and oddballs. My favourite catfish are the sturisoma festivum but I have about 8 different whiptail varieties at the moment. I adore oscars (I have one currently) and most SA cichlids. The Jaguar cichlids are amazing but I can't see myself owning one on space grounds but who knows. I have a small herd of Javanese medaka which I'm very fond of and 9 ctenopoma acutirostre which I absolutely dote on. Who doesn't love corydoras

I'm not a huge tetra fan but I love ember tetras. I'd keep more tetra species and probably get into them but I always seem to have fish that would either eat them or that they would harass.
Most African cichlids don't really appeal to me, not sure why. I think maybe because many look like marine fish and for some reason, although I like to look at marine tanks, I've never wanted to have one. Also, I don't like the general proportions of the fish, SA cichlids are a beautiful shape IMO and the Africans are too long.
Likewise, never got into the livebearers.
I always like to see stingrays and they are very interesting but I have no desire to keep them.