I don't know what I'd do without my Multitool (a tiny one at 1.9 oz.):
Pliers--grasp strap ends to pull through buckles (my fingers won't do it), use as pot lifter when cooking, some uses for fishing
Knife--cut things such as moleskin, fishing line, duct tape when needed as patches or adhesive tape, trim hangnails, cut thread if I have to sew, gut fish
Tiny screwdriver--tighten screws on my glasses, which I need to do every other day to avoid losing them.
Larger screwdriver--prying off lids of water bladders in dog's pack
File--file fingernails, which split if not filed daily

Without it, I couldn't adjust straps on my or dog's pack, couldn't remove pot from stove, couldn't cut tape, glasses would fall apart, couldn't get the lids off dog's water bladders, would have seriously split fingernails and even worse hangnails, etc. And I'd have to eat fish with the guts in