Tayous:
Over the years I tried a lot of different things. I still tend to pack two or three different means of fire starting in my kits. However, the one absolute best fire starter I've encountered is a Strike Force synthetic flint & steel.
Bics and other lighters crap out, run out of fuel, stop sparking, etc. Matches get used up or wet. Pistons are toys. There are other flint systems out there, but they often have fragile components that break, or have small diameter flints that crap out. All have limits.
I like the strike force for a few reasons. It is self contained: It has storage room for tinder (I use petro jelly/cotton balls and pack em in tight). The flint is large diameter and is therefore less susceptible to breakage or wearing out. It's stone axe simple, with no fragile components. And best of all, it throws a huge shower of large, hot sparks, making it easier to ignite marginal tinder.
End of the world, with no hope of resupply, and my go to starter is unquestionably the strike force. Long after butane has been used up, smaller flints have worn out, commerical tinder is gone, the strike force will be lighting fires for years to come.