If you could choose just one survival tool, what would it be?

Last night at dinner we were talking about the television program "Naked and Afraid". I have not watched it, our son in law explained that two people a man and a woman are set in the wildness with no clothes. They can each choose one survival tool to have with them. We bantered around what each person (there were 5 of us at the table) would want, matches, an axe, machete the entire list of stuff. I have a tendency to always go with water and all things water related. A filtering straw, a gallon of unscented bleach or purification tablets maybe. At least a cup to gather water in, or a pot of some sort to boil it in.
     I believe there is always some way to make a fire, I wouldn't be too concerned about that.

If I could find a cord I would construct a "friction"
type of starter. 

Likewise to be concerned about firewood is most likely wasted effort as well. What I believe makes the choice so difficult is the fact they have no clothes on, no belt, shoelaces or fabric from a shirt to use for various survival needs. It ends up the choices in tools that are made are it, that's all a person has. If I were to chose a knife, I would be able to cut things, vines, thin wood, construct a trap for game or fish. A tarp would be handy for construction of a survival shelter, but it's easy enough to build one with the logs, leaves and forest debris. A hand ax or a hammer have limited uses as well, I'm trying to stay alive here, so I want what will supply me with the one thing I can not live long with out. Water, I want it to be free from all the bacteria and bugs that make us sick, that means boiling. (Click here for a guide by the EPA) The three tools I feel I would need are 1) Something to boil water in, like a pot or steel cup 2) Fire, most likely I would use a friction type of starter I would be able to make with little effort. I would have to find a cord or vine for the bow. 3) Fuel, there should be a lot of it laying around.
     My decision is to choose a "Kelly Kettle", it's a coffee pot looking tool (see the photo) that has a double jacketed steel wall, and is open through the center. It was invented in the 1800's in the British Isle's for fisherman (one use) to heat water for their tea. It's a genius tool to use to boil water. The jacket is filled with water, then a fire is built in the base of the pot using the inner open area as a "flue", it acts much like a "Rocket Stove", but not as noisy. They use very little fuel, they don't appear to be more than about 50% efficient due to the aspiration of the expelled flue gases. But hey they work wonderfully and could easily supply water for several people for a long time. We don't have them on our web site to sell, regardless that would be my choice, a "Kelly Kettle".

     I would not like to be met with that choice, I would not volunteer to take part in a program like that, it's just not my style. There are many blogs, web sites and government programs making suggestions on what should be in an evacuation kit. I read one yesterday that was 30 pages long, I could not think of one more thing I would pack in that bag. There are others suggesting a quart of water and three matches, way out on the other end of the spectrum. I would always recommend going for the water, we can live 3 days with out it, less depending on the ambient tempurature, yes water.
     What would your choice be? One tool, not enough but a pretty good mind exercise.
Thanks for reading, comment and tell me what you think, Thanks!
jimandkate
emergencykitsplus.com