Quote Originally Posted by digiman619 View Post
Make up a mock sphere of annihilation; i.e., one that follows the same rules, except being touched by it causes the recipient to be his with a faerie fire effect that lasts for 1 round rather than being destroyed. Then have opposed caster level checks to control it like the actual sphere. Have the two be, say, 15 feet apart, and have the two will the sphere at the other. The loser is clearly identified (via the spell effect) and you can do best of three for the matches. This way you blaster and your diviner have the same chance of winning.
Magical Ping Pong, I like it.

To kick it up a notch, make them stand on a half-court together, and have to whip the sphere off of a wall of force, aiming to hit the other caster on the rebound. Magical Squash.