I'm not sure there's such a thing as an object that wasn't designed, but I chose glass jars for my non-designed object. Obviously, any logos included on the jar are designed. But I'm just talking about the jar, itself.
I like it because it can be as pretty (or not pretty) as you can make it, depending on what you do with it. It can also be used for serving drinks, holding flowers, storage, and more. You can even make a lamp out of it, or string up a row of them with light bulbs inside each one to make outdoor lighting.