If only one was allowed it probably would be the Blast Match. I always want at least one method which only takes one hand.

I'd probably pick my Bunker firesteel.

Anything with ferrocerium *and* built-in compartment for a tinder.

ESSE Fire Kit

StrikeForce (if weight and size is no object)

Or possibly something with magnesium block or rods like this one from TOPS.

road flare!

I made an off-the-cuff answer earlier that my one source would be a lighter, because that is my EDC.

But in reading here from time to time, I seem to be missing the thrust of this thread. I am guessing it is because I am assuming your EDC, PSK, and camping gear all include fire starting stuff, which means on a camping trip you are always carrying a "kit" with multiple options if you are ETS.

I would have, for example: an EDC lighter and key-chain striker-ferro rod; a PSK spark-and-tinder quick plus a few REI matches and strike strip; and in the camping gear more REI matches and strike strips in a match safe, another lighter, a knife-ferro-rod-magnesium bar, and a piezeo-electric propane stove.

Of course we all know when you assume, you can make an "ass" of "u" and "me."