I have carried a butt pack of some variety for over 40 years whenever I leave civilization. These trips include arctic, desert, and jungle environments; so I have fine-tuned my kit for wherever I might happen to be. I now carry it in my truck on the road as well. Here is what I carry in it:
First Aid kit
Bandaids of assorted sizes
Military cravat bandage for slings, head bandage, etc.
Tweezers large and small
Parachute cord/550 cord – 50 feet
small fixed blade knife
small folding knife
Emergency Bivy Sack from Adventure Medical Kits (much better than a space blanket)
A few zip-lock bags – 1 gallon size
TP – small roll
Fire starting kit
Carbide (mix with water to release acetylene gas)
Vise Grip pliers – smallest size
10 lb monofiliment – 25 feet
assorted hooks and flies
Military strobe light – 1 D cell battery – I change the battery once a year.
Zip Ties – assorted sizes
Trash Bags – 2 Large Leaf Bags
Small head lamp – 3 AAA batteries
This kit, added to my (always carried) pistol and extra mags and Surefire flashlight and the Victorinox and Gerber multi-tool and Gerber folder on my belt, has never let me down.
I swear that I will defend the Constitution against all enemies - foreign and domestic. Sargemsb