So many good points already! Trash bags and dental supplies are huge—easy to forget until you really, really need them. I’d add sewing supplies to the list. Might sound old-fashioned, but a simple needle and thread can make a torn jacket or ripped backpack usable again, and in a long emergency, clothing and gear take a beating. I keep a little tin with needles, sturdy thread, some buttons and safety pins, and even a bit of waxed dental floss (stronger than regular thread for repairs).
Another one for me is hand protection—extra gloves, not just for warmth, but for garden work, debris clearing, or hauling firewood. I’ve had a blister or two turn into real problems after too much work outdoors.
Funny about guitar strings—I don’t play, but I always think about comfort items like tea bags or a deck