The 5 C's of Survival
The Five C’s of Survival or Survivability, credit Dave Canterbury of Self Reliance Outfitters (known from Discovery shows such as Dual Survival and his book series on Bushcraft), are based on essential tools: a cutting tool, a combustion device, cover, a container, and cordage.
To some, a standard cutting tool from a multi-tool or pocket knife to a full tang bushcraft blade is top priority in their Every Day Carry *(EDC). The number of uses for a cutting tool are too many to list. The size of the blade and it's efficiency in any given scenario is completely dependent on several variables but a good rule of thumb is that with skill and patience a larger knife can generally do the same tasks as a smaller knife but a smaller knife cannot scale up and do the same tasks as a larger knife.
A combustion device, another no brainer - Fire is one of the most important elements in almost any survival situation and is, of course, what sets us aside from any other species on the planet. Warmth, cooking and protection; not to mention peace of mind due to its natural pest and predator deterrence. Always pack a lighter, matches or some kind of fire steel (striker) and exercise patience and careful planning whenever starting a fire.
Cover, as in shelter, can be anything from a downed tree to a camp. It's always a good idea to pack a tarp of some kind in your EDC so you can quickly put up a protection from rain no matter where you are: worst case you can always wrap yourself and wait out the storm.
A container: some real thought should be placed into this item. The right sized container can easily double for cooking and food, and the material will greatly impact the life and variability. With this piece of gear, you really do get what you pay for. Depending on carry capacity the best choice would be a titanium pot at around 450ml to 750ml but would not exceed 30oz ~ this way you can both cook and boil drinking water in the same container and limit your carry weight and increase your overall carry capacity. Titanium, however, is generally much more expensive than aluminum and is slightly heavier but is considerably lighter than steel and will stand up to any abuse you can toss at it.
Lastly, cordage. Bind a wound, tie up a shelter, fix your clothes pack or shelter, repair a tool, create a trap, hang something up high, bind gear together, and so much more! It's always a great idea to tuck away a roll or two of paracord or some type of strong synthetic rope that is resistant to the elements, just in case.
These, of course, are just the core elements of survival; depending on your environment and length of stay you will almost definitely need other resources, but with the above tools you should be able to keep yourself afloat while you either acquire or create whatever else you need.