For a language that likes to cluster a lot of consonants around a single vowel, Polish has a lot of word pairs in which the meaning is quite different (even completely opposite), but the orthographic difference is a single vowel, often simply the addition of "y":

The most troublesome is przeszłość // przyszłość — when explaining grammar in Polish to first year students, one slip of the tongue and suddenly you have some momentarily confused students. "But I thought this was a past tense, not a future tense!"

Of course if you're driving, wyjazd/wjazd might be disastrously confusing . . .