Killian Advertising has some atrocious cover letter “bloopers.” Except that they were done on purpose, so I don’t think they can be called bloopers. There are other horrible writing examples on other pages.
And, believe it or not, they say that college teachers often send them examples of terrible writing. They say it happens because the teacher grades it, the student doesn’t like the grade, the student goes to the dean, the dean chastises the teacher, and the teacher-untenured-sends it on to Killian. So beware of your writing appearing on the web.
I first read about it at the Cranky Professor.