I love cories but recently I've been watching my ghost shrimp alot. They seem so busy with their little claws warding away fish and then taking off and swimming up to the top to snatch food while the fish are eating. They strike me as smart little guys going about their business and then a fish swims by ten times their size and they breifly pause to threaten the whale with their claws and then back to foraging.
Corydoras & Danios (of any variety) because they are fun to watch. I swear they have ADD.
Bettas because they have such great personalities. They are the doggies of the fish world. Angels because they are so graceful and beautiful.
I really don't have a favorite genre of fish but I truly love my Featherfin Squeaker. It is so fun to watch, he swims upside down and chases the other fish out from under his rock. Seen it feed at the top a few times when I stuck in some freeze dried shrimp. There have been a few times when I've taken it out for water changes and he has just "squeaked" away. Its really cool to hear him talk, kind of sounds like a little mouse.