Knife–a few more essential uses besides slicing cheese:
Cutting bandaging material, sometimes just trimming the ends off a too-long bandaid or making a hole in a piece of moleskin.
Whittling "frizz sticks" to make fire when wood is wet. Has anyone ever needed an emergency fire when wood is dry? "Emergency" includes when the grandkids are out with me and want to roast marshmallows!
Whittling a point on long stick to roast said marshmallows.
Trimming broken finger/toe nails.
Cutting cord sections to replace busted shoe laces, tie rocks to tent guylines when the stakes won't go in, and many other uses
Tightening screws on my glasses (which are forever coming loose, and are much easier to repair before the screw falls out and is lost).
I can't get the foil wrap for Katadyn Micropur tablets undone without the knife!
Jason Klass uses his knife to dig a "cathole" but I would never want to ruin the blade like that.
You'll never catch me out on the trail without my knife!
The "Ten" Essentials (originally developed by the Seattle Mountaineers) are basically a list of stuff that certainly a beginner should never venture out without. I can get along without some, especially extra food since as a stout person I already have "extra" on my body! When you're backpacking, of course, all the "essentials" are already with you. It is quite possible for even an experienced person to somehow mess up while dayhiking and have to spend an unplanned night out. You may not be comfortable with them, but at least you can survive!