There are several outdoor equipment lists telling a daring hiker what to take onto a trip. One of the most comprehensive and undisputed lists is called The Ten Essentials. It was first published in the 1930s in a newsletter of a outdoor club from Seattle, called 'The Mountaineers'. Though it has been reprinted, changed, reduced, enlarged many times, the basic Ten Essentials have been an excellent tool for outdoor teaching for more than half a century. No one has ever made a statistic of how many lives were saved by the Ten Essentials. It is, however, not presumptous to say that most of the people who died from hypothermia, got lost and starved or fell to death might still be alive if they had had the Ten Essentials.

The original Ten Essentials are listed below. It has to be understood that it's not sufficient just to carry them. You have to be able to use them, too. They are not a guarantee for a safe return from the hike. Not taking them isn't a guarantee for not returning safe, either. There is no law saying "Take them all and you'll live, forget one and you'll die." Every single one of them just increases your chances more or less, depending on the situation:

Essential 1: Matches

Use only the 'Strike Anywhere' matches. All the 'Strike-on-box' matches work only with a dry striker strip on the box. If you lose the box ot the box get's wet, you have a problem. Unfortunately it's very easy to mix them up in the stores. Always check and double check whether they will light on some other surface. Don't trust the promises of the store. If it's a good store, they will understand your mistrust. If they don't, it's better to change stores.
If you are sure to have the matches you want, place them into a watertight container. There are different waterproof cases in the outdoor stores. Don't forget to include a striker as well. A piece of grinding paper will do for that purpose.
Matches, even when storen in a water proof box, weigh almost nothing, but are one of the most useful survival tools. If you get lost out on the cold and have to wait for the next day, it's not only the heat and light, but even more the moral boost of your little campfire that helps you through the night.

Essential 2: Fire Starter

Sometimes a good supply of waterproof matches just isn't enough. Unfortunately this tend to be the moments when a fire is crucial for survival. So it's important to have some fire starter with you. There are different kinds of fire starters, from liquid to solid. All of them work properly if you do not lose them!. Always store some fire starter with your matches and the grinding paper in your little waterproof box, but do not store that box in your pack! If you lose your pack (which is one of the standard problems, esp. when wading rivers) you're going to be in big trouble.

Essential 3: Map

A map, along with the knowledge how to use it, is the best insurance against getting lost¹.

Essential 4: Compass

When the Ten Essentials were published for the first time, back in the 1930, nobody even dreamed of GPS devices. A map and a compass had to be enough. Nowadays, as those little GPS things tend to cost hardly more than nothing, a compass seems to be outfashioned. Don't dispense with it. Compared to a GPS device, a compass really costs nothing. It doesn't need batteries, and it gives you exact bearing without the need to move. The GPS, however takes over the role of a compass more and more. If you have one, learn how to use it. Waypoints, "Trackback"- or "Man-Overboard"-functions can save lives.

Essential 5: Flashlight², Extra Batteries and Bulb

If your time schedule has not worked out like you had planned it, you may have to find your way back to the trailhead in total darkness. The only safe way to move through an unknown terrain in darkness is on hands and knees. This slows you down significantly. Carrying a flashlight (or headlight, that's a matter of taste) enables you to walk your way back watching your step. It's a good signalling device, too. Some of the flashlights have a strobe mode which attracts the SAR³ teams in a case of emergency. Don't forget extra batteries and bulbs.

Essential 6: Extra Food

Always carry some extra food with you. It's good to choose someting that's really a last resort ration, like dried dog food or pemmican. Shrink-wrap it and store it in your pack and never take it out again. You can, of course, survive for some days without food. Having some food, even some disgusting one, helps to keep your thinking clear and to avoid panic⁴. If nothing goes wrong, you should always bring some of your food back from the hike. Otherways you don't have enough of it.

Essential 7: Extra Clothing

Even the sunniest days get cloudy from time to time. You may be delayed due to unforseen reasons. You may have to spend the night out. Extra clothing is the most life saving of all Essentials, as hypothermia is the most frequent cause for trail deaths. Carry at least some kind of rain jacket⁵. It keeps off both water and wind which can drain your stamina even when you're not moving any further. As the center of the body heat regulation is in the head/neck area, always carry some kind of hat. An old but still valid rule says 'If you have cold feet, wear a hat!'.

Essential 8: Sunglasses

Sunglasses may be dispensable when you walk through a forest area on a foggy day, but they are particularily important when walking through snow or on white sand or rocks. Snowblindness will render you absolutely helpless. You'll have to be guided out, which can set you and your party at stake.

Essential 9: First Aid Kit

Emergencies can happen always and anywhere. Even the most basic First Aid Kit, along with the most rudimentary knowledge of how to use it, can make the difference between dying from or surviving an injury far away from professional medical help. If you just stumble and fall, causing some laceration, you may be able to walk your way out on your own feet if a First Aid Kit is at hand. If you can't, the First Aid Kit will give you and your party significantly more time to wait for help.

Essential 10: Pocket Knife

There's no need to carry an axe or hatchet. A plain and simple Swiss Army Knife will do. You can make repairs to your gear, chip splinters from some wood for kindling, cut blisters, open tin cans, cut fingernails, punch holes into a tarp, ....

Some other Essentials

Whether or not you have to carry some additional things depends on where you want to go. Winter conditions will require even more additional clothing, alpine environment will require ropes and other things, the crossing of rivers an lakes will require a life jacket, going to the desert sets the focus on the water supply, ..., but the forementioned Ten Essentials are, as their name implies, ESSENTIAL.

Essential Number Zero, the most important survival tool of them all: Your Brain!

No matter how well equipped you are, there is one thing that you always carry with you: Your Brain. So don't dispense with using it. Plan your trip carefully before you do the first step. Avoid unnecessary risks. Don't overestimate your abilities. Make sure that someone is going to miss you if you do not return in time, i.e. tell others where you go and when you are planning to return. Take any sound advice you can get. Believe what people who are familiar with the terrain tell you. They may be the ones who are sent out to bring you back. You can bet that they will not give you any advice that might lead you into danger and them on a search and rescue trip.