Justin has a clever post suggesting new company taglines that are honest. A few of my favorites:
PopTarts: Until you realize how disgusting they are, we’ll keep making them.
Samsung: Didn’t you mean to buy Sony?
Southwest Airlines: On your marks, get set, find a seat!
Ikea: One day you’ll be able to afford real furniture.
And one from the comments: Twitter: What are you doing? How about now? ...and now?