Stashed in: Brands!, LinkedIn, Marketing!, Logos!, Scrubs!, Best of Tumblr, Hilarity, Favorites
I busted up, thank you.
There are more on the Tumblr blog: http://honestslogans.com/
There was a 1990 movie called Crazy People that was pretty good:
In the movie, clinically insane people write brutally honest ad slogans like the ones above.