None. I've never carried a knife on my person except when big game hunting. Then it says in a sheath on my belt. I've lived a long time without necessity for a knife on my person. I can live the rest of my life without carrying one.
I own Solingen steel outdoorsman knives. However, I've gone almost completely Havalon:
https://www.outdoorlife.com/blogs/l...fe-you-need-skinning-and-quartering-big-game/ My recommendation Is to bring a metal container suitable for dulled Havalon blades. A heavy knife still has field dressing utility when necessary for deep cutting required for quartering big game.
I carry a filet knife inside of my tackle box. I never carry it on me. I can't remember that last time I've used it. We're catch 'n' release unless a fish will not survive. In very rare times I clean fish, I do so with absolutely no distraction.
A knife wound could become fatal, not merely by destroying a vital organ. An infection (sepsis, staph, etc) from a knife wound can be just as fatal.
Pepper spray is far better than a knife for self-defense. The most proficient knife attacker can't cut what he can't see.
Knife blades accumulate plethora bacteria. If you're gonna carry a blade, have access to lots of hydrogen peroxide, Neosporin, gauze, and tape. Whiskey is still good as a disinfecting agent. If you were to cut yourself, cleanse and bandage all wounds ASAP. Loosen and inspect wounds periodically for indicators of infection. If indicators of infection are present, hightail it to a hospital. If you're 30 miles from the nearest hospital and sever an artery, get your final affairs in order. You might have a few minutes of consciousness remaining.
Years ago, I watched a TV segment that profiled a woman (I doubt that she was 30 years old) who had cut herself shaving her legs. She blew off the cut as just another nick from a blade she should have discarded after its previous use. Very sad and tragic: from that otherwise insignificant cut, she contracted necrotizing fasciitis. She was dead inside of 2 days.
In terms of self-defense, a knife is deadly force. If I were worried about deadly force, I'll carry my EMP 3 9MM in urban environments and a TRP .45 ACP where mean critters roam. There's a reason cops are taught to shoot suspects armed with knives.
If you're gonna carry a blade, I'd recommend watching "Surviving Edged Weapons"
One last point: I completely get it for professionals who use knives many times daily as tools of their profession. For those professionals, please indulge me a caution: allow no distractions when using your knives to perform tasks of your professions.