No Shofar on Shabbat
The Sages decreed not to blow the shofar out of fear that a single Jew who does not know how to blow might carry his shofar on Shabbat in a public domain. For the sake of that single Jew, we suspend the mitzvah of shofar-blowing that year for all the people of Israel!
We haven't written up this one. Arutz Sheva - Israel National News has the full story — the link below goes straight to it.