This is my favorite tool since 1984:
It is a roofing shovel, but I love the angle and the straight blade and strong long handle. I use it for making trenches, weeding, putting in edging, normal digging jobs, and other odd jobs.
But another item, not sure it's really a tool, is what I am sitting on. This item keeps me dry (er) and warm (er) when sitting on the cold ground to work. It means I spend less precious energy staying warm and so I can work a good deal longer.
That's right, my trusty sheet of cardboard with a shiny label on the bottom side. I go through about 3 of them a year.
The third item:
The sleds. I have a whole fleet of them. Because I can't work standing, I sit. Not having to reach up to put weeds into a wheelbarrow or tote saves me a lot of energy and so I can work longer. So these are indispensable for my garden work.
Also in this photo, sitting in the chair, is my memory, also not a hand tool but it is handwritten... This is the notebook with all my notes about the vegetable gardens. With the severe cognitive issues I deal with daily, this notebook is crucial to any success I have in the gardens.
These are the adaptive tools I've figured out so I can do what I do here. Without them, far less would get done.