Rapala Heavy Duty body if you know you're going to be where you have power all the time. I used to be a fan of the 6" blades, lately I've gone the other direction, 9" because they have a little more flex and IMO/IME do a better job getting ribs out and leaving meat behind on the fillet.
Rapala Lithium when you don't have power. I like this knife w/Berkely 8" "Slim Blades".
I won a Wustoff that's very good, as well as an older Cold Steel Carbon V from the bargain cave, but, I don't know that I'd pay the $$ out of my pocket over the Rapala like Meelosh suggested. Rapala has the "thinness and flex" down pat. Run through a 2-person limit of walleyes with any knife and it should make a trip over ceramic sticks anyway.