A versatile, useful outdoor/survival staple is 550 paracord - 550 i the rated nominal strength in pounds and paracord refers to its original use in parachutes. It is comprised of inner white nylon strands, encased in a woven outer sheath. Th heath comes in a variety of colors, from bright to camo. There is at least one variety with reflective strands.

Nowadays there are several versions with a strand of flammable material, red in all the versions i have seen, and evidently there is another variety with an added strand of wire, presumably for making snares and the like.

I am of the persuasion that you can never have (almost) too many ways to achieve fire n I have adorned my packs and bags with zipper pulls, etc, fashioned from the fire starting types. Eventually it occurred to test these in advance of a crunch time situation to see how well they performed.

i have tried three different brands. They all seem to have a red strand which performs about the same. They light fairly easily and burn about like an ordinary match. They are quite susceptible to snuffing in mild winds. The red strands will not blaze up like gasoline or alcohol, but will support ignition of small tinder - twigs, pine needles, or similar.
Definite useful since you can hardly have too many ways to ignite stuff.

Aside from its fire potential, paracord is quite versatile -everything from shoelaces to clothesline to lashing tarps, just about anything where you want a light, reasonably strong cord. However, they have absolutely no place in any situation where human life is supported by cordage - technical rock or ice climbing or rescue systems involving rope. I have seen paracord suggested for use as rappel rope. this has ben tried in the past and people have died. Such advocacy is the height of irresponsibility.

Within it limits, p cord is a very hand, useful item. What other uses have you tried successfully?