also Fritos, hand sanitizer, dryer lint, don't forget cotton balls dipped in vasoline 🙂
but more to the topic,
I'm going to say cooking tips.
I'd be careful with dryer lint. If you've been drying synthetics, that lint will contain synthetic material, not good to breathe the smoke. And for cotton, be certain the garment is not treated to be fire resistant before using cotton lint.
Cotton balls dipped in vasoline are great for starting fires. And vasoline is cheaper than the lip balm someone else suggested.
Reusable menstrual cups are lifesavers for longer day hikes and backpacking trips! I've found you don't have to change them as often as other hygiene products, so you can spend more time enjoying the outdoors.
@Former community member - I have the same sentiment! They have been game changers for when I spend long days out climbing or paddling. I was thrilled when REI started carrying them. The more time I get to spend focusing on the exciting activities I'm getting into, the better!