Active med ball passing demands a certain level of concentration and as such, is a good antidote for those of us who are afflicted with various levels of ADD. (Given today's fragmented, multi-tasking environment, this includes many of us.)
In this game, set up a small group in a circle and choose a med ball big enough to be physically significant. (In other words, there should consequences to missing a catch!) Now start passing around the circle, but mix up the directions. In other words, pass left or right or across the circle at your whim. Once people are comfortable with this movement, start adding eye fakes and head fakes to the action. Make eye contact with one person, then throw to someone else. This increases the concentration demand.
Now, increase the challenge further by moving around the room at will. Fake a throw, step, turn and throw. Everyone has to be on full alert now. If you keep the intensity level high, players will enjoy a highly focused experince and break a sweat at the same time.