I have lots of "favorites" but this is probably my favorite "SA cichlid" (festae is close too...):
Fish: Uaru fernandezyepezi
Common name: Panda Uaru
Region: SA
Size: 12"?
Reason for choosing this fish: This is a gorgeous fish with striking contrasting coloration. It also happens to be relatively rare, and difficult to keep. They do best in big groups and require a large tank and blackwater conditions, and at $100+ a fish, this means they are quite a costly endeavor, especially due to their propensity for dying in aquaria.
Interesting characteristics: Coloration, rarity
Picture: Google
Fish: exCichlasoma(?) festae
Common name: Red terror, festae
Region: SA (most assume CA, but they are SA)
Size: 16"
Reason for choosing this fish: First things first, LOOK AT IT!
Female pictured in breeding dress is a stunning red, putting most SW fish to shame. Hard to find and always desired, reported to be hard to pair. Causes most cichlid keepers to drool.
Interesting characteristics: Coloration!
Picture: Google
Fish: Herichthys(?) bartoni
Common name: Barton's cichlid, bartoni
Region: Mexico
Size: 7"(?)
Reason for choosing this fish: Rare, striking breeding dress (as seen in picture), reportedly hard to keep
Interesting characteristics: Breeding dress is white/black contrast
Picture: Google
Fish: Amphilophus Trimaculatus
Common name: Trimac Cichlid, 3 spot cichlid
Region: El Salvador,Honduras,Nicaragua
Size: 12-16"
Reason for choosing this fish: Many fish have aesthetics similar to the pure bred Trimac making it somewhat difficult to secure a pure bred.
Interesting characteristics: male nuchal humps and almost metallic color
Picture: My juvenile Trimac and Google adult Trimac
Fish: Parachromis managuense
Common name: Jaguar Cichlid
Region: Central America
Size: Up to 16"
Reason for choosing this fish: why wouldn't you? Just an awesome fish!
Interesting characteristics: big mouth, beautiful patterns, shows a purplish sheen in the sunlight, amazing personality!
Picture: my very own Jag, 'Diego'