I have three rapala filleting knives that I use for filleting as well as cutting up deer. They have flexible blades and are pretty soft steel. My go-to hunting knife is a 35 year old Normark - use that for small game, birds, gutting and skinning deer. It's hard steel - takes a while to get an edge on it. A few years ago, I grabbed a couple of $2.97 6" filleting knives from a bin at the checkout at Vaugh BassPro for use in the kitchen. Not as flexible as the rapalas, but really good knives at a giveaway price. I sharpen the filleting knives with a pull-through plastic sharpener which has a couple of steel (carbide???) blades inside. The normark I sharpen on an oil stone.
I've given several nephews hunting knives. Buck fixed blades. These are good knives but the blades are brittle and can break. There's a couple of them been sent back under Buck's lifetime warranty.