I name most of my fish by name or category.
I have a betta named Fifi, because even though he's a boy, he reminds me of a pampered poodle. I have a rambunctious crown tail I named DeeDee Ramone becuase he is a punk. I have a female veil tail named Fatima.
Skunk botia: Boo Radley because he's a recluse, Blue lobster Babbaloo becaue I like saying the word.
Goldfish named Lunch Bucket and Dinner, Dempseys named Screwhead and Gussie, clown loach named Tony, because he reminds me of that tiger on the box of cereal.
I also have the Raspberries (school of rasboras) and the zippers (black neons)
Some of them have photos in My Tanks album in my profile. But I have lots more, just don't want to bore people.