Like I said, not gonna be a signature nazi on this one as the rules do not state that they must but I think after this one and when I get a bit of time I will redo the rules ( if that is OK ) to include that sigs must contain the forum ID of the member making them or of the person it is made for.
As for the one you pointed out it was technically made for a gaming forum, gunslingers.com as a general publicity sig therefore the inclusion of "gunslingers" was the ID