The Germophobe : They lead a personal crusade against the bacteria, viruses, fungi and dirt that exist everywhere. They dread ATMs, computer keyboards, handrails, library books, babies, you name it. The terror can manifest itself in disruptive ways: obsessive hand-washing, for example, or an aversion to others' touch. (Scientists debate whether there really is any reason to fear germs so much, but marketers of hand sanitizers do a good business nonetheless.)

The Nitpicking Nester : She swipes her shoes vigorously on the doormat even though she's planning to remove them and still vacuums before doing anything else. A sense of peace washes over her as she aligns the pencils on her desk. This home sanitation expert, who may take her habits to the office, cannot handle clutter, confusion or the slightest surprise in her physical surroundings. She might become incensed with a loved one who fails to return an object to its proper place. She may even decide to live alone.