The movie Crazy People featured a group of patients in a mental institution that came up with advertising slogans for major companies. "Volvo: Yes,they're boxy, but they're safe." And "Jaguar: For men who'd like hand jobs from women they hardly know."
And then there's Letterman's ads:
Campbell's Chunky Soup: just don't ask us why it's chunky.
Floss: so people that visit will think you floss.
Johnson & Johnson: because one Johnson is never enough.
White-out: you don't need this product anymore.
So now it's our turn! Come up with a slogan for a well known product.