I am assuming you are talking about a 72 hour survival kit. Your goal is to stay alive and attract attention to get rescued.

I would use my CamelBack as my backpack. It has a 100oz water bladder. Taking into account the rule of 3s and the fact I live in Arizona here is my pick of 10 items. I have ¾ of a gallon of water. The first 3 items and my CamelBack would probably keep me alive for 3 days in most of Arizona. I would have water, shelter, and fire. The rest of the items would make life easier.

1. HD Space Blanket with hood (poncho, wedge shelter, immediate heat reflector)
2. Leatherman Charge Ti (knife)
3. Ferro rod (Metal Match from County Comm)
4. 12 Coghlan’s Emergency Tinder (in mini zip-loc bag) (got to have fire when wet)
5. 36”x36” sheet of HD aluminum foil (boil water, cooking, fire reflector)
6. 2”x3” glass signal mirror
7. Petzl Tikka XP LED Headlamp (or Tikka Plus or Zipka Plus) with case (high, low, and blink)
8. First-Aid Kit
9. 1 gallon Zip-Loc bag (container to collect water etc.)
10. 50’ of ¼” braided nylon cord (don’t like parachute cord)

There is a task that will get you to thinking about what is important! I kept changing the list. I kept asking myself; would I give up all the items below this item to keep it? You have got to be able to stay warm and have water. Then being able to get more water and purify it is next. You can signal with a fire if you have to. It may take longer than 3 days to be rescued. A metal cup, pot, or coffee can would be better than the aluminum foil. A compass would be nice but I can find north if I have the sun, North Star, or a crescent moon to look at.