Back in the early 70's, when we'd drive past a roadsign that said "Signal Ahead", other longhair types in the car would inevitably lift up two fingers and say, "Peace, Brother!" Kinda got old after a while, but then, so did we....

A good old yellow-and-black American "Yield Ahead" road sign might look good posted on the Tower Of London, though.

My favorite that was actually there on purpose was a sign that said "Slow Children Playing" in front of a school for retarded youth.