One I just saw this morning:

If you see this car a rockin'
Don't come knockin'!

I first ran into that sticker in the hippie days. Usually on a paisley print, day-glo painted van; "if this vans arockin' don't be aknockin'".

Later it became, "don't laugh your daughter's inside."

"Power boats are for people not smart enough to Sail"

I actually saw these on hats, but I can add them here.

* self deleted one due to it may have been taken to be,
well, lets say uncouth.


and, this one, my wife doesn't think it's funny anymore, but I still recite it fairly often:

Everyone has to believe in something,
I believe...I'll have another Beer!

"Pregnancy a STD that lasts 20 Years"

If your lucky it's only 20 years. Try throwing them out of the house.