- a pencil
Show the pencil to the class--teach that the useful, best part of a pencil is in the middle. And in order for it to be useful, something sharp has to wear away the outer covering. Let's compare that to the heart/spirit that is found inside each of us.
In order to be of the most use as a servant of God, we allow God to scrape away our covering of pride and arrogance, and allow ourselves to become tools in his hands. After our pride is gone, the good part inside of us is exposed, and we are useful tools in God's work.
Source: http://www.geocities.com/Heartland/Flats/4746/lessons.html, with some additions by Jenny Smith