"grass is green" and "sky is blue" are always funny examples to me, since whenever I hear them I go check, and they're usually not true. Right now from my window, I can see brown grass and a white/gray sky.

So they're especially good examples, as people will actually use them as paradigms of indisputably true empirical propositions, and even those seem almost always to be a mismatch between the map and the territory.