Excellent topic. I will be watching closely to see what everyone lists.
I hunt from my truck, so my list might be a little different:
InReach: I hunt alone, and have heard/read too many horror stories of people getting lost / hurt / etc. while in the field. This is one item I never leave the truck without. Period.
Garmin Rino GPS: Almost got lost turkey hunting while in high school. I had on only light weight pants and no coat...it was getting dark and cold. Never again. Another item I never leave the truck without.
Leica LRF 800 Rangefinder: I'm a horrible judge of distance, and although this unit is 15+ years old, it's always with me. Optics are great.
Waterproof/breathable outer layer: including gloves and hat. Even when no rain/snow is forecast, this comes with me. Cuts wind, keeps me warm.
Essentials: license, knife, first aid kit, game cleaning gloves, extra bullets, leatherman. These items are always in my blaze big game vest. Love the layout and pockets. Even has rear pocket and compression straps to hold clothing. Great for when I want to travel light and not take my day-pack.