The examples I can first recall just now of decisions that I have heard people describe as "just common sense", are "Don't touch things that are hot enough to burn you," "Wear shoes when you go outside in the snow," "Don't break the law," and "Only eat when you are hungry ".
Each of these examples has a tree of exceptions and gray areas that leap immediately to my mind.
Having accurate judgement of "...hot enough to burn you..." requires a wide range of levels and kinds of experience in different circumstances. How long does a plate have to be out of the oven before the waiter can carry it safely using the specific towels or tools they have available to them? How long does a piece of iron need to be in the quenching water or air cooled after it has been red hot to be touched safely? These questions are meant to show that using this example of Common Sense requires some uncommon knowledge in order to practice it. So is calling it "common" just casual hyperbole?
That objection, or others, seem like crippling weaknesses to all the tenets I have considered as candidates for Common Sense, including "Don't be a supervillain."