This is the easiest modification to do but also one of the most useful. These are clip on so the only tools required are what you put into it. I got one at Home Depot and the other at Lowes. The HD one had a little pocket that was obstructing the loop so I cut the pocket out to allow me to hang a hammer (wrapped in yellow tape so I don't loose it in the woods). There are also two chainsaw wedges and a utility knife.
The right one has two crescent wrenches so I can remove my toothbar or open my chipper without hunting for tools. A folding saw and pruning sheers which are really handy if you are working around low hanging branches or vines and don't have a chainsaw handy. Finally a pair of linesman pliers and a pen.
I have found these are my most commonly used tools and it so convenient to have them right at your fingertips.