For general house projects, I’d say a Visegrip. I’m not saying it can do everything well, but it could be used as a hammer, pliers, adjustable wrench, and I’ve even used it as a screwdriver in a couple of situations. It’s not the best at any of those things, but it can do all of them if necessary.
Indeed a blade is one of the most useful things that you can’t replicate with naturally occurring items (a log or a rock can be used to hammer things, for example, or vines can be twisted into rope).
Opinel knives in particular are quite handy, thanks to the good quality of the blade. They can take a beating and keep their edge, plus they fold and fit in the pocket (up to No. 9 with ease), so they can fulfill the functions of fancier “survival knives”.
Add a ferrocerium rod for easy fire starting, and a good book for downtime by the fire, and you’re golden.
You should definitely check out knapping if you're interested in how people used to produce blades solely from natural materials. Knapped stones can even be superior to modern knives in certain respects (sharpness, shape for purpose, weight, etc).
It's hard to argue that a utility knife is one of the top tools. When I'm doing DIY and woodworking, the tools I'm most likely to have in my pocket with me are:
- Tape measure.
- Utility knife.
- Mechanical pencil.
- Distant 4th: Screwdriver.
- Even more Distant 5th: Linesman's Pliers (but I'm doing a lot of electrical work right now)
In particular, a few years ago I switched to the Milwaukee FASTBACK utility knife. They have a belt/pocket clip, storage for extra blades, and different models have additional features like: scoring, gut hook, wire stripper, bottle opener, and they have a new one with a bit driver built in, and they're cheapish at $10-$20. Early ones had a far-too-easy to press blade removal button, but more recent versions have added a metal tab to protect it.
On the screwdriver front, I went on a bit of a deep dive when Linus Tech Tips released their own $70 driver, which does look awesome, but in the end I decided I'm just not that picky and the one I usually reach for is the cheap "Amazon Basics 12-in-1". Fairly affordable at $13, and works fairly well.
I had started off the attempt to replace my ~20 year old multi-bit ratcheting driver (because the plastic was starting to break down) with a ChannelLock that Wirecutter fawned over, but I ended up hating that one, largely because it used ball bearings for retaining the bits and 80% of the time I don't get the bit fully seated and then the bit falls out. I also tried the Williams WRS-1 at the recommendation of Project Farm, and it indeed does have a much better ratcheting mechanism, more akin to the LTT, but in the end I decided things like a little bit of wobble and slop don't really matter to me when I'm using it. Having 4-6 Amazons that are just laying around, vs. 2 Williams or 1 LTT for the same price is probably more valuable to me.
"When all you have is a knife, a lot of stuff looks passably doable"