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.
A.M. Leonard Soil Knife
It seems like a good latrine shovel is an afterthought in backpacking. The ones you find most places are made to be lightweight out of crappy plastic. As a guy who hikes in the Colorado mountains year round those shovels have never been durable or multipurpose enough to dig a deep hole through roots and rocks when you don't have a whole lot of time because you gotta go.
This thing gets the job done. It cuts through roots and scrubby top soil, digs a nice deep hole, and still doesn't weigh an awful lot. (9 oz.) In the end it's also bad ass enough to double as a tool for self defense. I consider it a luxury item that's worth it for at least one guy in camp to have.
This app is a lifesaver around the fire when someone has a question no one has an answer to. Load all of wikipedia in your pocket and when someone wants to know who the bad guy was in "Speed" (Dennis Hopper, as it turns out, not Anthony Hopkins) you have the answer!
I haven't actually had a need for this in the backcountry yet but I've started carrying it anyway. In the days post jet boil the one thing I have ready access to all the time is boiling water.
This stuff is high density plastic that becomes like silly putty at 100C. That means you can boil it up in water, squish it into whatever shape you require and create anything you need. That should MacGyver you out of all kinds of situations. Break a tent pole clip? make one. Need a hand splint? go for it. Broken glasses? Fire it up! You get the idea. It's great stuff.
I've found it will even take screw threads. You can squeeze it around a screw or bolt and the plastic forms well enough that you can screw things in and out (gently).