I think it would be cool and useful, if there was a way to add the same category to multiple articles, all at once. Say there are 50 articles that are all female characters, instead of going onto each page to add the "Females" category, there would be some kind of "quick select option" that just allows you to add the Females category to all the categories.
I am an admin on the Suikoden wiki, and for those who don't know, Suikoden is a series of 8 games and each game has around 108 characters, and it took a while just to put all of the characters in the same category for each game. So I had thought, wouldn't it be cool if there was a way to add all of the characters into the same category with one edit?!