We haven't competed yet, or killed any balls with our robot during practice. But...
A few weeks back, three of the guys on my team were throwing around one of the 30" balls. The ball hit the corner of a rolling cart that was in the room...and popped. They tried to repair the damage first with tape and then with staples (!). Unfortunately for them, that didn't work.
Also, during human player tryouts, we were using a rolling gate that collapes like an accordion for our "wall." The points on top of the gate are rather pointy. One of the 13" balls hit the gate, and is no longer with us...
