What a fun idea! OK, here goes.
Five things I always have:1) Milk: Gotta have it. Nice way to add a few extra calories to a meal.
2) Eggs: Easy to keep, easy to fix. I usually have some boiled eggs sitting in the fridge so I can grab them and go whenever I'm running late or need a quick protein boost.
3) Produce (especially tomatoes and onions): Yeah, it's more than one thing, but the same thing always happens - I buy more than I really need, and end up adding them to all my meats and veggies in order to add flavor (and use them up before they go bad).
4) Oatmeal: It's a breakfast staple.

I make a whole pot on Sunday night, add fruit, yogurt, and nuts, and pack it up in Tupperware in the fridge for the rest of the week. Because I KNOW I won't have time to do it in the morning.
5) Spices: The ones I use the most are turmeric, cumin, coriander, and chilli, but cinnamon actually tastes strangely good in a lot of things you wouldn't expect. Add these to EVERYTHING.
Five things I sometimes have:1) Ground beef: Basic. Good for mixing with other things or making into hamburgers...
2) Chicken (not frozen...): I buy this in bulk, then separate it into little ziploc baggies and put the extra in the freezer. Somehow, it never makes it into the fridge in time to defrost for supper, though.
3) Fish: It's good for you. And tastes good if you season it properly. I get it when the price is right...
4) Tofu: Just sometimes. I like it.

5) Plain whole-milk yogurt: I'm picky, though. It has to be the right kind, and only one store in the area (not my normal grocery store) sells it.
Five things I want to have more of:1) Hot peppers: Serrano, Jalapeno, fingerhots, whatever...I always run out!!
2) Raspberries: I love these! Unfortunately, they rarely seem to be as cheap as strawberries, or even blackberries, and whey they are, the quality is often lacking. When I can get them, they're amazing by themselves or with yogurt. Lots of nice antioxidants, as if you needed another reason to eat them.
3) Good, homemade granola: Tastes great with plain yogurt, and maybe some fruit. I rarely take the time to make it, though, and it's probably overly carby even if I did.
4) Tea: Tastes good, and is good for you. I go in cycles with this. There's nearly always some in the house, so sometimes I drink tons, and other times I won't have any for a week.
5) Avocados: They taste good, and have nutrients and good fats in them. The problem is that I can rarely figure out what to do with them before they go bad.
Five things I'll never have:1) Potato chips: Greasy and nasty!
2) Cilantro: For some reason, the taste of this herb really bothers me...
3) Store-bought cookies: If I'm going to eat something this bad for me, I'd rather make them myself. They taste better that way!
4) Twinkies: Gross. I'll leave them for the little bug guy in Wall-e.
5) Hot dogs: Why do people eat those??