Nice one on the spark plug tip!
I think the modern variant of survival kits started out with John Wiseman and the like publishing knowledge mainly adapted to tactical purposes.
Altoids tins, and bug-out-bags are very useful if your're likely to crash your helicopter in the jungle, or being shot at while taking a dump away from your unit.
Of course any clear and present reasonably plausible danger, like earth quake or brush fires will be a good cause to have one as well.
For me personally, my only real EDC consists of tweezers and a tiny knife on my key ring, along with my cell phone.
On most days I carry a small vial of current meds.
In the wintertime, staying on top of the weather forecast, and not giving in to fashion is the best survival tip. At around -15 deg C, the morning commute can become a problem, with a late train, windy platform and not enough clothes. Proper clothes and shoes goes a long way.
I have for a long time been thinking there's nothing in my life that a short hike or a phone call won't sort out. However, someone on here wrote about badly spraining his ankle in his back yard and the troubles he had.
Getting close to 40 I don't feel invincible anymore, and I can think of a number of spots I frequent, where I don't have cell phone coverage, and nobody will happen to pass by in a short time. Including my own basement.
So maybe the means to stay warm while immobile and also means to fashion a crutch should be an EDC. Whats that, a bothy-bag, proper folding knife and some paracord?
On carabiners: When out, I use mine for hanging my pack around a tree in camp, and on bus journeys, to secure it against the baggage rack or poles or railings. It's embarrassing enough to be in backwood clothes, smelling of wood smoke, among city folks. I can do without my 20kg backpack crashing down into the isle, cookware clanging, and possibly spilling that bag of trash lashed to the rear of the pack that I haven't found a way to ditch yet...