If I had to be completely honest here, I would probably have to say the Svord peasant mini. I know it's not pretty, or refined, and doesn't have the best fit and finish, but it's 1.5 ounces, small enough not to scare anyone, is carbon steel so can throw a good spark and holds a decent edge, easily sharpened, has a small tang on the back so provides the strongest 'lock' on any folder I own, can be opened with one hand, and can be easily removed from the scales in a survival situation to create a makeshift spear if I needed it to. Not to mention it's dirt cheap. There's so many good things about this blade.
I mean it's not nearly as impressive of my Spydercos, GECs, or Le Thiers, but there's something primitive about this tool that just gets the job done. It can fill so many uses.