a big bull Parachromis Dovii would be a dream, although i would never have a tank big enough for one, I read on mfk of someone claiming to growing one up to 42" the official record is 36" I think.
They are basically a giant blue Jaguar with a kok and teeth the size of your average dog!
Realistically speaking there isn't really anything, I have kept most well known common species other the last 15 years (and a few rares), I'm just excited to see my living room tank (120g) at its full potential and everything at full size
Edit:
A pair of Amphilophus/exCichlasoma Festae would be something i'd love to keep thinking about it
theres another mean cichlid i like , Nandopsis haitiensis or hatian cichlid often called black nasty. apparently a well deserved name , reputedly 1 of the most mean aggressive cichlids around . even meant to be able to give dovii a run for their money , so it must be a bad boy