I relatively often meet 4 of these:
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no speed limit (use the normal limit for this type of road)
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car tires may defy laws of nature (slippery road, usually followed by a sign saying it applies during rain)
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speed camera ahead
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no water polluting goods (not very common, but occasionally comes up. There is also no dangerous materials with an orange trapezoid instead of an ellipse)
I also saw don’t drive off the pier (around ferries), watch for skiers (in the mountains with cross-country skiing routes), and warning about planes, although in different design (around airports).
A solution to this problem: https://www.youtube.com/watch?v=z9pD_UK6vGU