Memorable because I saw them in Seattle (the tree-hugger capital):

Cut out vivisection!
Poaching is Mutiny on your Bounty!

and then there's the classic:

If you can read this, you're too close!
If you don't like my driving, call 1-800-EAT-****
If you don't like my driving, get off the sidewalk!
My other car is a Rolls Royce (on a junker)