Having these things will make your life one heckuva lot easier post-collapse. Not to mention these items will be great to barter with if needed.

1.Bleach
It’s as cheap and easy as a cleaning agent gets. Once you’re out of bleach, you’ll definitely notice.
2. Soap
Without basic sanitation, you’re going to get sick fast, and ill is something you definitely don’t want to be when medicine is in short supply. The best tip you could possibly have in terms of soap shopping for post-crisis scenarios: try to stock up on soap that’s anti-bacterial.
3. Painkillers
Get some reasonably strong over-the-counter pain meds, and make sure you have enough to last you if the SHTF. Though painkillers have expiration dates, they don’t really expire. They get weaker instead, so don’t be afraid to stockpile pain meds just because of the expiration date.
4. Lighters and Matches
Really and truly, you cannot have enough of these lying around. Sure you can make fire without them, but it’s hard: really hard.
5. Toilet Paper
There’s a reason why this one makes it onto pretty much every list like this. Yes, it’s a simple thing, and yes, of course you can live without it, but you probably really won’t want to.
6. Scissors
You can have as many knives as you want, but when your last pair of scissors breaks, you’re going to be sorry. Scissors make cutting hair, nails, and a slew of other things one heck of a lot easier.
7. Screws, Tools, and Building Materials
Nails and screws are essential hardware materials. They go fast and are a giant pain to make from scratch. Make sure you have enough lying around while you still can.
8. Can Openers
The majority of stockpiles will have a very large number of canned goods, and without a can opener, it’s going to be difficult to get what’s in the can out without wasting a good chunk of the insides or cutting yourself trying to get that can open.
9. Ammo
You can never have too much ammunition. It’s also beneficial to stockpile arrowheads and bow strings.
10. Alcohol
Whether you’re personally into drinking alcohol or not, you’re going to regret not having enough alcohol when the SHTF. After all, think of all the people who would be willing to trade almost anything for a bottle of their favorite whisky or beer.

One thing that the list brings up that's definitely important is having something that's a tradeable commodity. This list has that commodity as alcohol. Stocking up on a bunch of those little bottles of booze that are always at the checkout counters of liquor stores is a great idea because it allows you to trade them individually for supplies with other survivors. Another great idea is toilet paper. Imagine life without toilet paper. Yeah, hoard that stuff like gold.

If you want to see more of this excellent list, head to More Than Just Surviving.