The basic concept is the *.

Be it an Asterisk or a Star this symbol represents exceptions and distinctions.

Within the academic field an A is widely known as a great achievment but and A* or A(star) is just that little bit better.

Within business and advertising the * is often used represent an exception, something that stands out and is important enough to need its own explanation.

This mark is minimal, adaptable and something that can easily become memorable.