WARNING!!! I am not trying to promote any sort of illegal behavior in any way, shape or form. I will be using illegal situation scenarios.
I will be purposing things that may have a medical impact on some people. DO NOT think I am giving any medical advice, but rather my opinion based on experience
I see a lot of threads on this forum about what to do when apocalypse whatever comes knocking. Seems to come up more and more often. Zombies, system collapse, Mama N, bla bla bla.... Weapons, food, shelter, water... All the majors come up, but there are some minors that I think need mentioning.
SALT. If you are on the run from zombies or are hunkering down for the "lockdown", salt is a good thing. Salt tablets if on the run, a bunch of sealed salt if hunkering down. If you are not in a salt producing area, this can be especially important.
MULTIVITAMINS. Probably some of the other major league supplements too. Again, your diet may or not be supplied with what you are used to and/or what you need.
MEDICAL OINTMENTS AND PETROLEUM JELLY. Good for lots of stuff. Im not a medical person, but IMO, a tube of ointment or ointment base is worth it's weight in gold.
CONDOMS. For on the go scenarios. Yeah, sounds funny, but they are perfect tiny sacks sacks for stuffing, and NOT in a sexual context. Small, individually sealed and sanitized, in it's fullest collapsed form, and can really be put to some storage use. And there is also the added bonus that if you hit an area that has already been picked, you will likely see these still on the shelves when other storage devices have already long disappeared. Plastic and latex gloves are good too, but are bulkier and would more likely to be picked sooner.
ASPRIN. Unless you know just what natures alternatives are for it, pick it up.
SUPERGLUE. Found all over the place. Excellent for a lot, including it's original purpose of sealing flesh.
SEEDS. So often I see short plan, or if longer plan scenarios, the problem of food comes up. After a while if you survived the initial whatever, "easily" gotten foods become way the eff harder when it comes to wild gathering for a lot of people. Seeds properly stored can last for years on most of the "essential" crops. If you are stumbling around in holy crap land, don't just seize that produce you recognize. Save the seed if you can.
HAND TOOLS. We use a lot of powered tools. Not a ton of hand tools are required for a base set of usefulness.
THE DEWEY DECIMAL SYSTEM!! Yep, this is one you could know right now. If you are effed and don't know what to do about X, you local library is an excellent resource. And who in the heck hits the library when things are all apocalyptic (outside fortress lockups)? You don't necessarily need to know what's in those books now, but it sure can be helpful to know where you are looking for when time is of the essence.
In our current age of electronic resources, don't forget about our non electronic look up systems.
I know, it's nutty. But I think if it really hits the fan there are a lot of basic things often glossed over in the name of media hype scenarios.