Usually in mine its toilet paper, extra zip lock bags, some paracord, water, extra hat, a snack, deer gutting tools, niwalker crazy flashlight, thermacell (early season), chem hand warmers. I just haul it in my back and climb up with it. If I'm in my climber i'll haul it up on my haul line instead of wearing it up.
I also wear a fanny pack with some other items... hunting license, tree stand fall recovery strap, extra tree step, pen, extra zip locks, 5hr energy drink, maybe a granola bar, grunt tube, xbow cocker, car keys, extra batteries, a couple knives, head lamp, backup flashlight, etc..
It really depends on what time of year, your anticipated sit time, and the weather. If its colder I'll bring extra layers to throw on. Even when its early season, you can walk in and get sweated up on an afternoon sit and get REAL cold when the sun starts to set. Having a hat or a light jacket really can make those sits comfortable...