There is no tool which can replace good training, and good training can replace most tools. Everything is situation dependent, as Susan points out, but with the right knowledge and training, you can survive most anything. Attitude is VERY important, and I agree with MostlyHarmless about the book: "Deep Survival". The same concept is taught in most DOD survival schools. If you have prepared mentally (knowing the environment you are going into), and have an attitude that will not let you give up, you can survive. "Know more, carry less".