The only way I can answer this and keep it to five is to play with the definition of the rules.
For example, I'm going to say my tool belt, or my cordless battery. By default, if I have my tool belt, I have everything on it. And the battery itself is not worth much. however, the things it powers...
For the record, my daily carry tool belt is 6 items: pruners, soil knife, pocket knife, flashlight, pliers, 11in1 screwdriver.
what are the things I'd highly recommend for yard/landscape/small farm/homestead?
push pull hoe. not a scuffle hoe, not a stirrup hoe, a push pull hoe. triangular in shape, flat. I used to rely on scuffle hoes or stirrup hoes. I happened across a yard sale with a flat hoe in a design I hadn't seen before. so of course I had to take it home. It sat for while...it was older, handle was in rough shape, i have no shortage of tools. I was an idiot. The first time I used it, I won't say it was a religious epiphany, but I'm telling you...if you think wire weeders/scuffle hoes/stirrup hoes are great, you have got to try this thing. I don't leave home without it.
pine straw rake. a few years ago, we had a tropical storm come through. it left a mess in terms of branches and pickup. such a mess I was motivated to find other ways of getting the job done. What I found was a pine straw rake. I keep finding new ways to use it. thatching, debris pickup, yard leveling, seeding prep, and best of all...you can do it from a tractor seat.
stein arbor trolley. kind of a niche tool. there a few competing things in the marketplace, no two quite exactly alike. There's a reason I selected this one over the others. It was designed to be pulled by hand and to get branches/logs through gates and across yards where you couldn't take equipment. I have a list of modifications to make, the first is to extend the drawbar and put a tow hitch on it. It's something I use practically every day and keep finding new ways to use it.
if shovels are a part of your life or work, I recommend a nursery digging spade. Mine has a steel handle. I can dig a hole in asphalt with it. It slices through roots like butter, and I use it as a pry bar far more than I should. Actually, who ever gets away with using a shovel as a pry bar? My brand of choice is king of spades, mostly because it was the first such one I ever used, from A.M. Leonard. It's heavy. Mostly, it does the digging for you. I hand it to someone and they nearly drop it. After they use it, they want to keep it. It's another one of the things I don't leave home without it.
I am continuously surprised at the number of people who don't know what a soil knife is.