agree with a lot of what some have said. long time ago I spent a very cold night on top of a mountain without bivi gear--it wasnt too cold per se, but even cuddling for warmth we froze our asses off and were feeling pretty rough the next AM trying to find the sketchy, loose rappel gulley so we could get home. Of the injuries I've seen hunting and playing in the mountains, only a few have been trauma--most have been weather related cold injury, hypothermia, that sort of thing, and a few have been burns. I figured out at some point that I could easily duct-tape a space-blanket inside the space between my climbing helmet and it's harness, and combined with the invention of LEd headlamps all of a sudden realized I could fit quite a lot of "oh shit kit" into not much space. I actually found a small nalgene water bottle that was like 2/3 of a quart, a little smaller than standard size, and I put my entire emergency kit in this--it protects everything, keeps it dry, and doubles as water-carrying in a pinch, and the whole kit is very light and compact. This isnt everything, but here are a few of the things I HAVE used from the kit over the last several years when things did not go as planned, that I either didnt see mentioned already or that I consider essential:
1) headlamp
2) spare batteries for headlamp--lithium are lighter and last longer and dont age as badly as alkaline
3) hemostats for pulling quills (mostly for my dog so maybe not as important deer hunting)
4) duct tape--I wrap around a pencil to save space, great for blisters in a pinch, repair, etc.
5) spare hipbelt buckle--I've used like 3 of these over the years, it weighs nothing but saves the day if a buckle breaks
6) did I mention a headlamp? Probably my most-used emergency item
7) pencil and paper--have had to leave notes or send a note for someone in emergency or to avoid a potential scare when they were expecting me to be somewhere waiting for them, to send someone for help able to clearly communicate an injury to first responder, etc. (cell phones have changed this, but still many areas near my home with zero cell service)
8) a length of cord to open a conibear trap (again, for the dog)
9) small leatherman, mostly for the pliers
10) snickers bar, only to be eaten in emergency