As for the carabiner, it's perfect for a lanyard to keep any piece of essential gear (knife, multitool, kit bag, or even USB sticks) firmly attached to your person. Each bag or kit of mine has several
Granted that toy biners are handy for that purpose, in a survival kit where you are concerned about weight and bulk, I ditch the biners and use an all cord, adjustable lanyard tied with a double fisherman's knot. The DF knot is formed around both sides of the loop, giving you an adjustable figure eight lanyard.