I may leave the computerized antler-scorer and the bag of trail mix at home, but I am never without the two most useful items any hunter can carry–duct tape and parachute cord, or p-cord, or 550 cord. Between these two items, there is almost nothing you can’t fix, rig together, or make work for just a little longer.
Duct tape (not “duck,” for God’s sake; why would you tape a duck unless you’re some kind of pervert?) can be used to put up targets, close major cuts, cover holes in radiator hoses (at least for a little while), cover holes in cabin walls where the wind is coming through, pad the points on caribou antlers, and repair cracked gunstocks.
P-cord (called 550 cord in some circles because it will withstand a tug of 550 pounds) can lace up boots, wrap knife handles, hang bagged moose meat in trees, make a belt, make a rifle sling, rig a temporary shelter, replace the crummy leather hanging loops in rifle cases, serve as temporary reins, make a tourniquet and, if you’re having a really bad day and want to see what’s on the other side, you can hang yourself with it.
If you throw a Leatherman Wave into this mix you can probably save Western Civilization as we know it.