The first is a means of communication. Life is so much simpler if there is simply a way to call for help. Modern cell phones are the greatest boon to survival since fire, in locations with coverage.

The second great need is fire. For signaling, for warmth and to keep critters away, fire is a key. When in doubt, start a fire. It increases the chance you will be spotted and the flame will raise your morale. Exercise caution, in a survival situation the last thing you need is a raging forest fire.

Once those two immediate concerns are out of the way, we can address the other needs.

High on the list is a sharp knife or axe. Don't worry about fancy serrated edges, a knife isn't going to have teeth set like a saw, so a hacking motion is better than sawing. You can cut brush for fuel for the fire, cut splints or create a spear. You can clean and carve any animal you might need to consume. There is a reason why every culture on the planet has developed knives and hatchets.

Some sort of first aid kit is a wise precaution. This should include dressings and bandages, a topical antibiotic and cleanser and supplies needed for any special problems such as allergy to bee stings. Special kits with fancy contents are probably not worth it, stick to the basics and learn to use them without needing to read the instructions.

If you know how to read a map, carry a good map of the area showing relief and elevation. With a good map on reasonable terrain, you won't even need a compass to determine where you are, but elsewhere plan on a compass or GPS. In a survival situation, the best advice is usually to stay put, but if you are hiking or hunting, knowing where you are can tell you what to do next.

If you are camping, and intend to be out for days, there is obviously need for potable water, food and an appropriate form of shelter. Exposure to the elements can kill all by itself, so means to stay dry and out of the wind is important. There are plenty of options for a wide variety of needs, from sleeping bag covers to keep snow and rain out up to large tents for teams. Food ranges from concentrated survival rations through dehydrated foods on up to conventional canned products, with military field rations available for those willing to spend the money. Clean water is not an option. Diarrhea kills.

Especially for a hiker, the weakness you can suffer after drinking contaminated water can prove fatal, by preventing you from walking out of an otherwise safe situation.