Here's a list of essentials to have on hand:
PARMESAN CHEESE: The whole point of cheese is to extend milk's shelf life. Some types of it will not go bad at room temperature. Should mold appear, just slice it away; mold cannot penetrate the interior of cheese because it needs air to grow. Hard cheeses such as Parmesan, Manchego and especially pecorino have the added benefit of being extremely salty further discouraging spoilage.
NUTS: Nutritious, delicious, filling, versatile.
CRACKERS: Bread can last a few days; crackers last much longer.
CANNED BEANS: Cannellini beans, black beans and chickpeas are so versatile. Have them on hand for Italian, Latin-American or Middle Eastern dishes, or make a three-bean salad.
ONIONS, LEMONS, GARLIC: None of these fresh products require refrigeration, and they can all be counted on to add immeasurable zest to whatever you're whipping up.
PEANUT BUTTER SUBSTITUTE: Tahini (sesame paste) and Nutella are protein-rich shelf-stable spreads. Stir some tahini into mashed beans, and you've got hummus; use it to give a twist to canned tuna. Smear Nutella on a cracker and call it dessert.
CANNED FISH: In addition to the regular, water-packed stuff, there's canned salmon and, for the stout of heart, sardines. Add a mashed, jarred anchovy to almost anything to subtly deepen the flavor.
OLIVE OIL AND VINEGAR: A drizzle of extra-virgin olive oil or a splash of good wine vinegar elevate most foods.
The preceding list of foods will put you well on your way to always having dinner. Add pasta, canned tomatoes, eggs, butter and parsley, and you're ready for company.