Lentils- red and green
Pasta- tons and tons of different shapes, and please- wait for the good quality Italian stuff to go on sale and stock up. No one's life is long enough to waste part of it eating gummy pasta.
Canned tomatoes- I prefer whole, so you can make a lovely red sauce, but diced are great for soups
Canned beans (I just don't remember to cook beans, so I don't pretend that I will soak them then crockpot them then have them on hand)
Kidney beans and cannellini/great northern beans are great for salads. The cannellini can also be used in place of garbanzos in a hummus recipe.
Black beans are great for taco salads and soups- not to mention punching up a scramble.
Pinto beans, because I am from the border, are what the baby Jesus cried out- refry them, use them to make bean soup, put them on taco salads, in burritos- they're the bestest.
Rice- I usually have brown basmati, basmati, jasmine, and arborio on hand.
Spreads/fancy little things you've found on sale. Olive paste, mixed with some olive oil, garlic, and chile flakes, makes a delicious fast pasta sauce- perfect, really, for angel hair.
That's pretty much it, for bare bones stocking. A couple bits of fresh veg, tofu, or tempeh every week, and I am set for snacks.
Spices are my big splurge. I can't function without cumin, smoked paprika, and cayenne. I prefer to have lots of different curry powders and generic "Italian seasoning" around too- it takes all guesswork out of cooking when you're just hungry and you want something easy and fast.