For me, I love catfish, as they all seem to have quite distinct personalities. Catfish tend to be on the larger side. The fish that I have seen with the most distinct personalities are also those that have a genetic predisposition to grow large - when you're a child, you don't mess with adults, because they are so much bigger than you. As you get bigger, you get more curious, and find that you are threatened less by the world in general.
Fish which are less threatened by the world tend to be more outgoing...
Larger fish are generally less skittish, more likely to actually respond to you personally, such as associating your appearance with food - and therefore more likely to provide you with interaction - rather than being a swimming thing in a box in your room, they become individual creatures - and their individual welfare becomes important to you. I would rather look after a fish than a tank...
