Rather than get all 'survivaly' with my carry on items, I tend to go with just a few items that are very likely to come in handy while flying, and some might be good if something goes bad.
My main priority is multiple means of charging my phone and my wife's. You may be stuck on an airplane for many hours longer than you anticipated, and not all planes providing charging ports. So I carry two lithium battery packs, one that will recharge one of phones five times, and the other can about two and half times. I take at least three USB cables that I already know to be of good quality (a lot of cables out there are junk). I take two wall chargers capable of outputting at 2.0 amps for the fastest charging possible. I usually take a USB voltmeter/ammeter as well to verify that my devices are charging properly (this has really come in handy).
If space allows, I really like to take a 6' extension cord with a 3 outlet tap attached to it. This allows me to plug in and charge all my stuff at the same time without having to be right next to an outlet. I've never once seen anyone else in an airport with an extension cord. In a pinch, it could be used as stiff cordage or even made into a flail with something heavy on one end.
I refuse to pay $4 or more for a bottle of water, so I take a Brita plastic water bottle with a built in carbon filter with me. It's empty when we go through security, and I fill it up at a water fountain or bathroom in the airport. I've learned that most airports' water taste horridly, and this filter really improves the flavor. I always fill it up before I get on a plane.
Lighting is another important area, and I keep a small LED flashlight in my pocket when we fly. My wife keeps one in her purse as well. I like headlamps too, but they are bulkier, and we usually travel light.
Beyond that, I think that others have already covered the basics. Adhesive bandages, meds you are likely to need while traveling (Pepto Bismol tablets help many GI problems), and the like are always a good idea.
It's worthwhile to mention that I was not allowed to take a 'tactical' looking pen on a flight because one of the ends was somewhat pointed and I was told it resembled a kubotan. But a regular metal pen would be just fine and largely serve the same purpose.