I'm a believer in a pack
I started using a pack many moons ago and don't know if I could function without one now. First, by having all of my incidental items organized I literally grab my pack and my gun and I'm gone. My buddies are fumbling around trying to remember where they set their flash light or grunt call while I stand there laughing. I have a good size pack but it's far from full for a reason. If I am stand hunting and know I have a hike to get there I usually don't wear my coat. That get's tucked in the pack and I minimize the sweat factor. Nothing will get a guy colder than having all your cold weather gear on and walking 3/4 - 1 mile heating yourself up only to freeze in your own sweat for the rest of the time on stand. As far as must haves in the pack, I have a flashlight, grunt call, rattling bag, knife, paper towel, cover scents, gloves, neck sock, range finder, water, and a few extra rounds. If I am doing an all dayer in the woods, a lunch gets thrown in as well.
If I am going adventuring, I have been know to grab a few things and hide my pack close to my stand so that I can go as light as possible when I still hunt. Just so you know, I am an expert at hiding things in the woods. I have pulled gutted deer next to a dead fall, covered them with sticks, branches, and leaves and made them disappear. I took a buddy back to a hidden deer to help me retrieve it and he could find it 5 yards away from him. He thought I was pulling his leg until I reached over grabbed a leg and jerked out the buck.