Write the following words in big letters on a board or flip chart:
Tell everyone "You have 30 seconds to get in line in order of how much confidence you have in your public speaking skills. I don't care how you sort yourselves, just do it."
Line them up so they can see the words you wrote on the flip chart or white board.
Say, "Describe yourself for at least 30 seconds without using any form of the verb 'to be.' If you hear any of those words, make an alarm sound and the speaker goes to the back of the line and gets one more chance. I'll go first."
Use one of the "to be" words in your third sentence.
Make your best alarm sound and point to the person in front of the line and say, "Go."