Favorite I have: Either my Kribs or my fearless yo yo botia loach.
Favorite I've seen SCUBA diving: I don't know what it's called but I bet someone here might. I have never seen it more than 3 or 4 inches. It is sort of shaped like a damsel, is deep dark navy blue with tiny polka dots that are a brilliant baby blueish/teal color. The dots stick out so brilliantly, it looks like they're glow in the dark or back lit or something. It is my dad's favorite and he always points em out when we dive together, so there is some sentimental affection there too. Plus I like how small they are and how they have distinct "homes." Anybody know this fish?