A diamond is different to every person, it doesnt really matter what is popular but what you like and looks good, dont go by the fancy names and ideas given by companies like cherry corals and unique corals because they are jsut a rip off. If you see one that looks good and is just what you were looking for, just go for it. Red planets are cool, borealis, bali slimmer, hawkings are all cool acros. Montipora setosas and confusas are rare and cool but they grow extremely slowly and their price also represents that. Pokerstar minti's and supermans are nice as well, but again it is your preference.