Let me back up a bit. McCutcheon first offers a definition of mania: "an excessive enthusiasm or obsession for something or someone; craze." Now consider the list he offers (minus the ones I thought were common, standard, or just wouldn't work in a novel):
Believing one is a genius (I can see the comedy in this one...)
Urge to kill
As I typed the list, I thought of several ways to use these, but I'll admit my mind is running toward the humorous. The "enthusiasm or obsession" can run both positive and negative. For example, someone who's manic about books could either be a zealous collector that's pushed to a hoarding level, or someone who's terrified of books and refuses to crack a cover. Think how rough this person would have it if he were a college student or a librarian. Or the woman who's manic about bathing. She's either bathing thrice a day, or once a month. Both could have humorous or devastating effects on the character.
What did you think of when you read the list? Did anything stand out to you as highly useful for a character in your novel?