I would second the dwarf cichlids, they are abit rarer..meaning you wont find them at petco/petsmart for the most part. IME most fish will interact to some degree, the fish that interacted the most with me was a green sunfish, he actually seemed to like me being around. The oscars are second, my convicts pairs are interesting to watch, the way they interact with each other is amazing, almost like they know what the other is going to do, especially in defending their babies.