This is my personal collection of weird stuff I carry when backpacking that most people don't. Throw yours in the comments.
A simple light weight charging kit for iPhones or other USB charging devices. It takes off the shelf AAs you can buy at the gas station on the way up the hill (or uses more environmentally responsible NIMH batteries) so the weight easily scales up or down based on your trip. Last time out I got my phone from 40% to 100 on 4 AA's. It's not the best energy density by weight, but you can't beat the price.