I always keep a mosquito head net in my bag. It's light, doesn't take up a lot of room, and can save your hunt.
Don't forget your binoculars.
Chapstick, surgical gloves for easy cleanup, extra glasses if you wear them, a trash bag, and a dose or two of Aleave or ibuprofen. A head or back ache can ruin a hunt.
“He grouped his last five shots right in the center of the bull’s-eye. Then I showed him my technique of scattering shots randomly around the target because, as I explained, you never know which way the deer might jump just as you pull the trigger.”