Always pack an extra layer.

A small thermos with something hot (buillion) in your pack if it's cold can save the day

Tnhunter444 said carry something to mark the blood trail (#14) - I carry an extra ziplock back of toilet paper for this (note, I said "an extra bag") - white TP stands out in the woods if you're marking the trail, and is quickly biodegradable. I know some guys who use surveyor's tape (neon plastic tape) and it's highly visable, but anything that you don't pick back up stays in the woods for a long time.

I take a cheap stylus (you can buy one at the office supply store for only a couple of bucks) and attach it to some paracord so that I can text my hunting buddies without taking my gloves off. We don't text often, but sometimes it's good to let them know something is coming their way.