The circle with a dot in the center is perhaps one of the simplest and most incredible of symbols. The circumpunct has been used for an incredibly long time. The symbol once was a representation of the sun, and as such as been the symbol to represent the Archangel Michael. The circumpunct is also the alchemical symbol for gold.
Perhaps the most profound meaning for the circle with a dot in it is that of God. I had a professor once who had asked the class to draw the best representation of God. There were some students who drew Christ, others an old man in a chair, and then there were some that drew the Hindu gods. In the end all he did was draw a circle on the board with a dot in the center.