Top on my list is to catch one of each cutthroat subspecies. I have 4, about 10 to go.
Then a golden trout (in its native range), a Dolly, a bull trout, and an Arctic char, a grayling and that probably tops off the coldwater fish.

For warmwater i would probably look for a smallmouth, which i will be chasing this year.

Size doesn't matter; a pretty, colorful fish will be just fine.

I hope to get all of these on flies; eventually on one's i have tied myself.