Split your group up into smaller groups, and give each group a banana, cutting board and plastic knife. Each group should cut the banana into 4 or 5 equal sized pieces. (don't tell them what the next steps are at this point).
Then hand out banana surgery kits - pins, string, sticky tape, tooth picks, rubber bands etc. The goal is for each group to reassemble the banana.
The lesson from this game is that some things (relationships, trust, reputation, bananas!) are easy to break but more difficult to put back together.