Re: What is your one fish
Coldwater = rainbows, especially if that includes steelhead. I'm always amazed by how much fight even a 12" rainbow can provide! Of course, I say this without ever having tangled with a salmon on a fly or anything like arctic char, bull trout, etc, so that could change things...
Warmwater = probably a tie between smallies and northern pike... love the way they attack flies, and the fact that they are active around here in times of the year when trout streams get too low/warm and the migratory fish are out in the Lake Superior.