Wired Magazine lists its Top 10 Outdoor Survival Tools.
They are:
10. High-Calorie Protein Bars
9. Flashlight
8. Whistle
7. Backpacker Hammock
6. Water Purification Supplies
5. Plastic Trash Bag
4. First-Aid Kit
3. Metal Cup or Can
2. Butane Lighter and Tinder
1. Knife
Reminded me of Survival kit in an Altoids tin. Wired’s survey was less concerned with space.