If your goal is to torture other fish, id agree go with the black rhom. theyre feeding habits are pretty crazy. But other than feeding I personally find them pretty boring, they are skittish towards humans and dont have much personality.
If you want a true "wet pet" that you can interact with i still say dovii would be your best bet. look at balton's http://www.youtube.com/watch?v=iSMXR3UV2GI