Some of the wittiest things I've heard came from bumper stickers. I think it's because space is so limited--you have to keep whatever you're saying short and to the point. Anyway, here are some of my favorites:
I Fought the Lawn and the Lawn Won.
I Suffer Occasional Delusions of Adequacy.
God Made Us Sisters, Prozac Made Us Friends.
If They Don't Have Chocolate in Heaven, I Ain't Going.
Veni, Vidi, Visa: I Came. I Saw. I Shopped.
Princess, Having Had Sufficient Experience With Princes, Seeks Frog.
What If The Hokey Pokey Really Is What It's All About?
Liberal Arts Major . . . Will Think For Money.
Gravity . . . it's Not Just a Good Idea. It's the Law.
If You Want Breakfast in Bed, Sleep in the Kitchen.