1: A GM/DM who Lives and Dies By rule 0. Often cannot do anything without invoking it.
2: A Member of RPG forums who uses rule 0 all the time In rules discussion, contributing absolutely nothing to the Thread. Often uses it as an excuse to justify pushing his personal feelings as the right and proper thing to do.
Normal person: According to The designers of the book, It is acceptable to do this.
0tard's response: Well I do it this way, And I can because of rule 0, and I think everyone should too.