For X, it's all about the look and the mystery. X has to be given props for it's many sci-fi uses where it can thrown into with any generic word and make it cooler: Formula X, Weapon X, X-Wing. See? You wanna start dissin letters, how about W? Double-U. It's just copying another letter twice, pft! I don't know why it's not called Double-V because that's what it looks like.