A lot of good suggestions so far. Maybe you could go with a large male Red Devil. He will interact with people, and is definitely a beautiful fish to watch swim around. People will most likely get a kick out of him flaring up and defending his tank as they draw near.
I think you are better off going with a single speciem tank. like a single rhom, high fin banded shark, exotic pleco (L25), ray. That what tank mantanace will be a brease and you can get a bigger fish.