Back when I was teaching elementary school phys ed, I tried to figure out a way to have the fifth and sixth graders play this, but I didn't actually have enough faith that each class wouldn't end with a half-dozen missing teeth and bloody noses.
In general, I've found medicine balls most useful when used for their main purpose - as a heavy thing that can be thrown. I mostly use it as a conditioning tool, the old "throw and chase for time." 10 or 15 minutes of throwing a 8-10 pound ball all sorts of ways, running to it, and throwing it again, gets brutal. I picked this drill up many, many moons ago here:
The medicine ball slam is also one of the most challenging ab exercises I've found, if it's done right (actually using the abs and not the back/shoulders/arms).