I've completely changed how I think about SHTF knives.
I sold all of my thin, short bladed fixed blade knives. I don't want to bother carrying a fixed blade knife if it is not thick enough to baton wood with, and a specific blade length between 4" and 5". The only things I use the fixed blade for are food and fire preparation, and shelter making.
Anything short of that, I can do with a pocket folder like a Spyderco Delica or Endura, that take up half the space as an ESEE-3 or similar would.
A Spyderco Delica and a Bark River Bravo 1 worked great this Summer for every hike and camping trip.
Not even going to get into knives for fighting, other than to say that in prisons all over the country people are constantly killed with sharpened toothbrush handles and nails wrapped in tape. It doesn't take black coated blades, tacticool designs, or magic steel.
Opponents with knives? That's why we have Glocks.
Ever try force on force with a training knife and an airsoft pistol, at close range where fights start?
A pistol is only dangerous in a straight line from its barrel, and it runs out of ammunition. A knife is dangerous to the touch, and is much harder to deal with at close range.
I've known a number of folks that spent time in the joint. ALL street type fighting, whether armed or unarmed, is about going to work quickly and efficiently.
There was a book written 20 or so years ago called "Put 'em down, take em out". It was 50 pages or so, and is long out of print. The book was about knife fighting techniques from Folsom Prison, and was pretty shocking to the martial arts community at the time. Most martial artists don't know what to do in response to a 'sewing machine' style knife attack, when they trained with a willing opponent who stabbed once then sat there to let them work their magic.
Here's a good clip about what a knife attack is likely to look like: