Saw this one in downtown Naples, FL where we probably have as many or more Rolls, Mercedes, Porches etc. per capita as any place in the world, attached to the bumper of a rusted-out, early 60's Chevy:
My other car is also a piece of shit.

Also noteworthy:
Give me ambiguity or give me something else.

Horn broke. Watch for finger.

And one my ex-wife had on her old beater, the aforementioned "My other car is a broom." How true that was.