This script will alter the topology around a given point on a mesh to arrange 8 points in a circle. Useful If you want to punch a hole or extrude a tube shape from a relatively planar quad mesh.
The points around the center vertex need to have a rather uniform distance, it will fail if the quads are elongated.
It will orient the circle points according to the surface normal orientation, however, if you have rotated the object, you need to freeze transforms for the script to work properly.
You can have more vertices arranged in a circle as long as they are part of the faces that share the center vertex. I'm working on expanding the functionality of the script.