I keep a pair of scissors attached to one. I add small S-hooks to the tethers so I can add, move or remove tools easily. The layout is nice since the scissors fit nicely in the slot right near the tether. For now that is the only one of the four that I use. I am really used to having most everything on my vest but may eventually move some more things to the tethers. I think about moving my camera but so far have not. Same thing with pliers. It just seems more convenient to have them in my vest.
I never did have my scissors on my vest. On my 2011 Outback I used to just tether them to the handrail with some 100lb braid. When I look at the tethers I think of it as being useful for attaching something that you only care to use on one side of the kayak. Scissors fits that bill for me. However, for most things, I think I prefer being able to easily use something off either side of the kayak by having it on my PFD.
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Fish tremble when they hear my name

A ship in harbor is safe -- but that is not what ships are built for.
--John A. Shedd, Salt from My Attic, 1928