Sunglasses and Sunscreen
Sunglasses and sunscreen are important for staying healthy and comfortable on the trail and are useful in all seasons, including winter. While we all understand how important protection from the sun can be during the warm summer months, the reflection of the sun off the snow in the winter is just as hazardous. Sunglasses can help prevent snow blindness and protect the eyes from flying debris or errand tree branches. Sunscreen keeps the skin from being fried by the suns ultraviolet light, but remember to apply it well in advance, as it isn't much good after you've already been scorched.

Extra Clothing
This is one of those items that most people tend to forget about, but once again it can be a potential life saver. Carrying extra layers can help protect against hypothermia and allow for some versatility should weather conditions change unexpectedly or some odd accident occur. For instance, you could be hiking along a river bank, slip and fall in, and suddenly find yourself soaked to the core. Depending on the weather conditions, and the distance you need to hike back to safety, extra clothing could quite literally be the difference between life and death. Many climbers caught on a mountain during a freak storm have learned this lesson the hard way while others have survived because the brought seemingly unnecessary gear with them on their trek.

First Aid Kit
This one may seem like a no-brainer, but it is surprising the number of people who hit the trail without even some simple band aids in their daypack. Your personal medkit will likely vary depending on the length and nature of the hike, but it should have, at the minimum, the ability to treat simple cuts, abrasions, insect bites, and burns. I personally have several different first aid kits of varying sizes that slip into my pack on a moments notice when I'm heading out on an adventure that is more than a couple of hours in length.

Headlamp/Flashlight
Having a source of illumination may be the last thing on your mind when you start out on a hike in the bright morning sun. But once again, unforeseen consequences could prevent you from making it home before dark, and if that should happen, you'll be glad you packed a light to help find the way. A headlamp works best as it leaves your hands free to help guide you along in the dark or to carry other things, but a flashlight will do nicely in a pinch as well. Modern lights are efficient, bright, and inexpensive. Add a small one to your pack and chances are you won't even notice that it's there, but you'll be glad it is should the need arise.

Matches (or Lighter)
Depending on weather conditions, the ability to start a fire could potentially save your life. Bring either a set of matches or lighter along on your hike just in case. If you do bring matches, be sure they are either the waterproof variety or stored in a good waterproof container, lest become useless in a sudden rain storm. The ability to start a fire might not be just for warmth however, as it can be used to signal a search party as to you whereabouts should you become lost or injured in the backcountry.

Firestarter
Matches or a lighter are only part of the equation when it comes to building a fire, as you also need something that can help you quickly and easily ignite whatever it is you're burning. Once a match is struck, the best firestarters will burn easily and for more than a few seconds, while providing plenty of heat to get things going. There are a number of good firestarters available, including dry tinder but one of the best that I recommend is a few cotton balls soaked in petroleum jelly. This is an easy, cheap, and very lightweight solution that also happens to be highly effective.

Knife/Multitool
A knife has always been an a very versatile tool to have with you on any extended hike. They can be used to shave wood for the fire, cut through cloth or rope, perform minor field surgery, or even slice the evening meal. Modern multitools, such as the Swiss Army Knife, can do all that and a lot more thanks to the fact that they often incorporate multiple blades, screw drivers, cork screws, scissors and more. Those tools can be used to repair gear on the go and offer more options for when those unexpected occurrences crop up once again.

Extra Food and Water
Finally, you should never head out on to the trail without bringing some extra food and water along with you. Even if it means simply throwing a couple of energy bars or an extra sandwich in your pack, you may be glad you have them should your day on the trail extend longer than expected. Hydration packs and good water bottles have made it easier than ever to bring plenty of water with us as well, but you may also consider packing some kind of water treatment option too. A bottle of iodine tablets can make most water drinkable, even if it doesn't help the taste or a device like the Steripen Traveler, can be invaluable in this area too.

So there you have it it. The classic list of the ten things you shouldn't leave home without on any hike. There are a few other recommendations that could be added, such as insect repellent or an emergency blanket, as well, but this is the list in its purest form, and the one that most hikers and backpackers follow when preparing for their next trek. Perhaps you'll consider each of these items carefully before preparing for your next trek too.

What other "essentials" do you put into your pack?