Also in the excellent signage category, but with no photo to illustrate: A block club sign on the West Side that had a list of don'ts. "No drugs. No Loitering. No Littering." And then there were a few items that had sub-points to further explain.
No gang activity
--no threatening behavior
The design and grammar of the sign would have you believe that gang activity consists primarily of cussing and threatening behavior. I think Lester Freamon would disagree.