Pemmican and Hard Tack are my two favorites. The easiest is Hard Tack. If you make it right, it won't be TOO hard to just munch outright. The good thing about hard tack is salt. You need to replace it when you sweat a lot, so add a tad more than 6 pinches to the recipe, or use sea salt.

"Those who are able to see beyond the shadows and the lies of their culture - will never be understood, let alone believed, by the masses" - Plato