Core competencies are something I think about a lot. I love to dig into what makes companies or ecosystems or social groups tick. Especially when that core competency *enables* what they do:
McDonald's, for example, is a real estate company that happens to make burgers.
Walmart is a shipping logistics company that also sells things.
What other examples can you think of where the core competency of the company is such that the "thing" a company does falls out naturally as a consequence?