A few must-haves:
Ammunition.
A water source.
Plenty of potato seed. (Note: the spuds you buy in the grocery store are treated with a chemical to keep them from sprouting. Stock up on certified seed until you’ve grown enough yourself to provide a continuous supply for your family’s use and to plant next year’s crop. You can plant the treated ones, but only a tiny fraction of them will grow. Once they do, of course, you’re on your way to building up a seed stock that isn’t treated. You will, of course, have wasted an entire growing season or two to accomplish that. You might get real hungry in the meantime.)
Plenty of wheat seed, and a good stock for daily use.
A good stock of all kinds of heirloom (not hybrid) garden seeds of all sorts.
A grain mill. (Some will work on electricity or with a hand crank.)
If you have the place to raise them, chickens and hogs. Those are two great sources of protein that can, if necessary, fend for themselves quite well feed-wise. The hogs will also provide the fat for producing lard for cooking and soap for cleaning, two really important needs for any household.
A good woodstove, preferably one you can cook on if necessary, along with a reliable source of wood. Better make sure you have the tools set aside for cutting and splitting it as well.
For the moment, my HOA frowns on livestock, so I've got lumber and rolls of wire in the garage to make pens with when things start heading so far south that those rules will go away. I just got my first rabbit, who's a pet, but her offspring won't be.