I always like a bit of supply insurance. Might be growing up poor</teeny_tiny_violins> with parents that grew up during rationing that makes me distrust easy times.
I like Ryvita as a long-life bread substitute. Keeps ages and tastes pretty much the same even when it's out of date. Tasty with cheese at any time.
Peanut butter: doesn't keep forever, but long enough and pretty nutritionally/calorie dense.
Baked beans: a meal in a tin, food of champions, especially cold from the tin.
Tinned mixed bean salad: tasty, and five a day-ish in a tin.
Tuna: I feel bad for helping rape the oceans, but tuna's a regular meal here and tins keep for years. Not that they get much chance.
Mayo/Salad cream: when the margarine runs out you want something to moisten your Ryvita.
Tinned Sweetcorn: because I could live off tuna/sweetcorn/salad cream sarnies (or mixed with crushed Ryvita) for months.
Microwave brown rice: roughage and useful straight out of the packet if there's a power cut.
Tinned curries/mince&onion/etc. Surprisingly tasty in many cases, and calorie dense.
Tinned veg: never as tasty as frozen, but I always have a few tins tucked away.
Ginger Nuts! Because Megan shouldn't be the only one who gets a tasty treat during militia lockdown. They keep for ages and aren't so moreish that you scoff the lot too soon.
Dried pasta: keeps forever. The date is irrelevant. Not much fun to chew if you can't cook it or soak it for six months though.
Porridge oats & dried fruit: Healthy and can be left overnight if you can't heat up your porridge. Or use the oats to attract birds if you're short of protein.
Long life milk: but test it before buying much. Tesco's own brand makes a lousy cup of tea. Aldi's is better.
Tins of evaporated milk: useful if the milk runs out, and I'm a child of the 70s so evap is still peak treat in my world, especially on Corn Flakes.
Granola type cereal. Roughage, tasty, keeps for yonks. Can be eaten as a snack or turned into porridge.
Water: I got caught up in one of those mains burst supply losses once. No fun at all. So I always keep a bit in. Not enough for loo flushing or a water canon to disperse looters, but enough to avoid peak queuing times.
Dog food: Because why waste my precious baked beans on the rest of the family? (Also, we have a dog).
The freezer always has loads of frozen mixed veg in it, bread, and a few ready meals. But I don't rely on the freezer... the food in there would be eaten first if things got complicated.
Instant coffee: Because life isn't worth living without coffee, even if I have to eat the granules out of the jar.
Optional extras:
Candles: Because I remember the 70s power cuts.
Worcestershire sauce: condiment of champions. Useful for spicing up crow soup, pigeon pie, or <D&D>rat on a stick</D&D> if society breaks down or Tesco run out of hummus.
Ibuprofen: my currency of choice for the new economy after The Collapse. Lighter to carry than gold, less dependent on a functioning internet and folk stopping laughing than Bitcoin, and more useful than an AR-15 once your bullets run out.