Which is the most important letter in the whole Torah? Maybe the first one? Or the last? Do you think there might be one letter that the Torah just can't do without?
If any single letter of the Torah's 304,805 letters is missing, the whole Torah scroll has to be wrapped up and put away until it is fixed. So if someone asks you, "What’s the most important letter in the Sefer Torah?" the answer is, "Every letter is!"