Everyone's "basic" pantry really depends on what they like to eat, what they're cooking on a day-to-day basis, and what kinds of "surprise!" entertaining they may have to do at the last minute. However, there are a few general categories of things (in bold) that I see in almost every pantry, with differences in the specific type:

• Dried pasta - Pasta lasts along time, especially if they're made without eggs. You can't really go wrong if you have something long like spaghetti or fettuccine as well as something short like penne. From there, get fancy.
• Grains - Like pasta, these also last a long time on the shelf. The most common grain is rice. Mine is a mostly Asian household, so we have the Asian-style short-grain white rice. Since I'm trying to maintain some semblance of health, brown rice is gradually replacing the white rice, and we also have barley. A lot of people also like to have oats on hand for breakfasts and baking. Good idea.
• Beans and legumes -  I'm a huge cheater here. Long cooking dried beans are the way to go here, but I love the convenience of canned beans. I would say that black beans and whatever bean you put in soup (navy? pinto?) is good to have on hand, and of course, a can of chickpeas for an emergency hummus.
• Vegetables - Better to stick with frozen vegetables over canned, with the only exception being whole plum tomatoes. But for my Mediterranean bent, sun-dried tomatoes, brine cured olives, artichoke hearts, capers; bamboo shoots and water chestnuts for the Asian side.
• Meats - canned tuna (packed in oil, it tastes better). Canned salmon is good for a change, and of course, I love anchovies. I can eat those straight out of the can. By the way, Spam doesn't count as meat.
• Oils - Canola oil for deep frying, and olive oil for you know, everything else. I also have sesame oil. For reason, please see "Grains."
• Vinegars - Plain white vinegar at the very least, but I'd toss that for Balsamic any day. I also have rice vinegar for all the Asian cooking I do.
• Salt and pepper - obviously. I have Kosher salt, regular table salt, and soy sauce.
• Flours and other - all purpose flour at the very least. I also have whole wheat flour (in the freezer) and panko breadcrumbs.
• Stocks - for those times you don't have three hours to boil bones, chicken stock and vegetable stock, but not in cans

That should do it for a basic cook's pantry. Baking, on the other hand, is a whole different animal.