I know this one's been brought up a million times before, too, but can we please include extraneous apostrophes on the list of things that are painful to read? You do not "watch the horse's" while they are grazing in the field. You watch the horses. Plurals and possessives are not the same thing, end of story.
My peeve is folks who think the word "factoid" means a short, interesting fact. Factoid's traditional definition is "an untruth perpetuated by the media which is generally accepted to be true." Some dictionaries are giving up and having a second definition which is diametrically opposed to the traditional definition.