Just in case anyone hasn't caught my drift, for those who follow and may misunderstand, let me make it perfectly clear:

I do Not recommend using Cadweld or any of the flammable/explosive materials mentioned to start fires. Fun to contemplate they are simply too bulky, heavy, and inefficient to routinely carry and potentially too hazardous to used in any situation short of a life threatening need to start a fire, and a complete lack of other alternatives.

If you had them on hand, and there were no other way, you might use them as a last resort. Otherwise everyone is better off limiting their use to trained personnel using them for their intended purpose.

Lighters, matches, ferro rods, the old battery and steel wool trick, sunlight and a lens, even road flares, are safer, and more practical.