I don't understand the M4 recommendation...
He's looking for something that stays sharp, is tough and will take a beating. It is not particularly stainless, but the one I have has been used in wet conditions and never shown the slightest rust, not even on a razor edge and I just used it without regard to protecting it from anything. If I had something in the few months I had had it that needed cutting I cut it without regard to what I was cutting or cutting on. I did nothing to keep it from rusting. It stayed shaving sharp until I shifted it to a steeper edge angle, and has stayed shaving sharp since then.
Will it rust? I have heard of it but not seen it. Is it tough? IMO very. Will it stay sharp? Mine has.
I hacked up a bunch of cardboard, cut a fair amount of Kevlar, cut meat and fish, and did nothing but wipe it off. That works for me.
Hey, I congratulate you on finding "the" knife for you. I've had several of those "eurekas" and even have one I call the Magic Knife so know how you feel.
Am actually a fan of the M4 steels in their bailiwick, just don't think the OP's needs fits any of those.
Would love to have a friendly discussion around your thoughtful reply above, but don't have enough info. I've experience in M4, CPM M4, Micro Melt M4 and S690, with knives from 2 factories, 3 other makers, and myself. Can you provide the steel, maker, hardness, surface treatment, etc so I can respond?