RE: the one thing you can't live without???
Most- One of my sons. (or both)
Next- Folding stool and blaze orange "quiver" so I can carry it.
Others-(not in order of importance) Camera, pelvis saw, water, snack, extra gloves, extra socks, map of property, and heavy duty cord or light roap.
I always use a blaze orange upland vest because the game pouch is handy to carry some of the stuff.