I had all of the teens stand on the log in a straight line. From that position, they had to reverse the order of themselves on the log without touching the ground. It was a great no-setup game that forced the youth to work together and in close quarters. It took several tries and different techniques, but they eventually pulled it off. If you try this, a log isn’t necessary; any narrow space will work, as long as it’s close to the ground (for safety reasons) or above water (for awesomeness reasons).
My reason for the post is two fold. First, this was an activity that worked well for me and it might be something you would want to try, if you are in the right circumstances. Second, you don’t need any preset activity for good team-building, just get creative. Look at your surroundings. Find a task that is difficult or strange, and set some rules on how the group must achieve it and go. As long as it is something someone cannot do alone, it will foster teamwork. As long as it is safe, I say give it a go.