Oscars are very intelligent fishes, recognise their owners, are very impressive and hardy in fact they are like dogs in a fish body
You can also teach them to do tricks.
I would go for a giant gourami or a large cichlid. You could always have a few Oscars if tank size isn't a problem. A fish I would really like, even though its saltwater, would be a panther grouper they look sic as and apparently interact with their owners but they are hard to get ahold of.