I was screwing around on my server. This is kind of fun for a DM map. You now have to anticipate movement so that the trajectory and timing is right for the balls.
ball_life 5
ball_speed 500
bouncy 1
bounceback 2
sv_gravity 100
The balls bounce slow, the balls move slower than you, you float slowly, and you can semi-fly! Don't run into your own grenades!
*Note: you're not supposed to increase ball_life, especially if you're on an Internet server, since the game will start to lag/freeze. It worked fine for me with 3 people at ball_life = 5 on a 1 mb/sec+ connection. Setting it at 10 started to freeze the server for half a second occasionally.