Depends on the other fish.
If you are starting with the needs of a centerpiece fish and building the tank around those, then a Discus would be incredible. They need a temperature in the 80s, acidic water, and very clean conditions though with twice a week water changes. These are strikingly beautiful, large, intelligent but gentle fish.
For a more traditional community of smaller fish that won't fin nip, a Pearl Gourami would work well. They work well even with fairly small fish.
Another good choice for the general community is the Bolivian Ram (Mikrogeophagus altispinosus), not to be confused with the German Blue Ram (M. ramerezi). The German Blue Ram needs the same conditions as Discus and is fragile, but the Bolivian Ram does well in a wide range of temperature and pH, and is hardier. Rams are intelligent bottom dwellers that can tell the difference between individual people and are interested in the world outside their tank.
If you had peaceful fish that were of both of moderate size and won't fin nip, such as Corycats, Hatchetfish, Platies, Swordtails, Scissortail Rasboras, larger Rainbows, etc. you could try an Angelfish as the centerpiece fish. This is another intelligent Cichlid, but it will eat small fish and should not be kept with fin nippers. Angels are very graceful fish.
While they aren't traditionally considered centerpiece fish because they hide fairly often, I also find that my Longfin Albino Ancistrus functions as a centerpiece fish. They get to 5-6 inches, and Longfins are really lovely. Lemon Bristlenoses and Super Red Bristlenoses are others that are easy to see and so could function better as a centerpiece. The standard Bristlenose colors are so good at camouflage, though, that you could be looking right at them without seeing them, so I would only recommend the more unusual bright coloration for this purpose. Bristlenoses are excellent algae eaters, won't bother even free swimming fry or tiny fish, and are tough enough as armored catfish to be kept with more aggressive tank mates as well.