For a teamwork based challenge that will push you to your limits, try The Tough Mudder! It is exactly what it sounds: an obstacle course covered in mud, that will require you to work with your teammates to achieve victory. There are a variety of options, including the un-timed challenge series in different distance and difficulty levels, as well as timed races, the most difficult of which last through the night! If you are interested in challenging yourself to the max with a group of friends, family, or coworkers, think about trying The Tough Mudder! There are runs available throughout the year, all across the country. Check out their website HERE to see if they are coming to a city near you!