I always have a knife on my ammo belt, a 5"-6" blade. Carbon steel, takes a razor edge, can be used to skin if really needed.

Useful for cutting biltong, salami, bread, meat, twigs, ropes, sticks, all sort of stuff - including one's fingers...

Another great blade is the French Opinel: no-nonsense foldable knife, with a locking ring and one of the easiest blades to sharpen. Rusts, is ugly as a boar's ass, but does the job every single time you need, and better than fancier - and more expensive - knives.

Almost everybody I know carries either a fixed or folding knife, 4" to 6" blade.