OK. I don't care what your motivation is. Terrorists. Nuclear war. Global warming. Jenna Bush as president. You want to have your list of supplies on hand for when ....
THE SHTF.
Food - start with the basics.
Canned, packaged and dry foods. Canned anything as long as you eat it.
Medium-term length survival foods - Flour, sugar, salt, cooking oil, yeast, beans, rice, vitamins and protein powder.
Long-term - long term survival foods like Ready Reserve, MRE's, Emergency Essentials, whole wheat, dry milk, honey and cooking oil.
Food final - arable land, a garden, seeds, good soil, even a bunch of pots and a compost heap. Anything which allows you to grow more food.
Water - the essential!
Water. A well, rain barrels, a catchment system, a cistern, water barrels to fill now for later.
Water filters and purification systems including filters, a pump and lots of plain bleach.
The ability to dig a new well, sandpoints for a hand hammered well, a nearby lake, stream, creek or river.
Power/Fuel - got to keep going!
Wood for the stove. Gas for the truck. Solar or wind for the home. Propane or diesel for the generator. Batteries for storage. Gas for the stove including propane, butane or natural gas.
Medical - Stay healthy or what to do when you get sick.
Other the counter medicines, lots and lots, starting with apirin and working your way across cold and flu season, allergies, bug bites, sunburn, anything which can be painful, deadly or harmful.
Herbs to substitute for manufactured drugs.
Protection
Firearms, ammunition, bows/arrows, knives/swords/axes, clubs, sticks, stones and chemicals.
Hardware
Building materials, filters of all kinds, batteries, tarps, buckets, nails and other fasteners, tools, spare parts, rope, wire, flashlights, lanterns, tents, campers, cook stoves, bedding, hammocks, sleeping bags, and anything else which can be obtained from a hardware or camping store.
Cleanliness!
Soap, shampoo, tooth paste, disenfectant, bleach, cleaning supplies, toothbrushes, toilet paper, paper towels, tampons, towels, and razors.
Finally, lots of common sense, prayer, religion, faith, hope and courage.
You can call it from there. If I missed something, well, drop me a comment.