I like the series of posts by Jon Miller on Ambiguous signs (another example). Here is a sign that got my attention recently and they succeeded in keeping me away (which I think was their intention).
Photo in Johor Bahru, Malaysia near the Royal Palace by John Hunter.
The area is near the Royal Palace in Johor Bahru Malaysia, though I am not certain that is what the restricted area is. It isn’t obvious to me why this location requires shooting trespassers, but I took the idea from the sign to stay out. To me, this sign conveys pretty forcefully that you shouldn’t consider entering if you are not authorized to do so.
Related: Living in Malaysia – bear warning sign on hiking trail – Visual Instructions Example
