That would be cliche.

Name the fresh and saltwater fish you have not yet caught but would give up your first born to lay into.

For me it would be a California Golden Trout and a Permit. (My topic - I'm allowed to break the rule.) Second to a permit would be a Dorado I think - cool looking fish - tasty too.

I suspect some might say a sailfish or marlin but I'm not sure I have that much interest in fighting a fish for 6 hours - at least not at this point in my life. I do however reserve the right to change my mind tomorrow.