I Have "Yes it's fast, no you can't drive it" on my roll bar and "I'm not tailgating, I'm drafting" on the license plate ring.
I have really enjoyed the "Bad Cop...No Donut" sticker.
In No Cal,there are many idiot stickers that espouse any and every crazy cause but "Nuke the Whales" and "Visualize Whirled Peas" also bring a smile to my face.
For the Nuclear Chemists in the group, "Heisenberg May have Slept Here" was seen around the Washington Beltway.
Back in the 70's, I saw one that said "Honk if you love Jesus". I honked and he gave me the Finger.
For the Dislectics amoung us, I saw "Dog is my co-Pilot" recently.
Jim