Grammodes - predatory looks, big heads, interesting colors
Cuban - very striking when larger, sort of like a small managuense
Hemichromis elongatus or frempongi - gets to around 7 inches, cool shape, piscovores with fairly large mouths
Mayan - get larger than the others, but underated. when you see them in fish stores they look drab. feed them hikari bio gold and lots of krill, and they color up nicely
Salvinis are cool fish, love them. But for a single fish aquarium, I think they may hide too much. Despite their nasty tempermants, they are kind of shy.