Stepping on egg shells:
Many are accustomed to abstain from stepping on egg shells due to danger. Accordingly, egg shells are not to be thrown in areas that people walk. There is a story dating back to the Rebbe Maharash regarding this matter.
 There is no known source against doing so, other than the story of the Rebbe Mahrash, and accepted custom
 Shemuos Usipurim 1/73 tells over that the Rebbe Maharash once passed the inn of Yitzchak Shaul in Lubavitch and noticed egg shells laying in front of the inn. The Rebbe went on to warn Yitzchak Shaul that in the future he is not to throw egg shells in areas that people walk, as it is forbidden to walk over them.