On another forum I frequent we raised over $50,000 for charity this Christmas by instigating ban wars.
1: You could pledge $10 to get another poster banned for 24 hrs.
2: Before the nominee got banned they could respond by bidding $20 to have the pending ban annulled, and ban the person who paid for them to be banned for 48 hours.
3: If a person was nominated for a ban by multiple people, they could bid $40 to anull their ban for 24hrs and ban *all* of their nominees for 72 hours.
4: These people all had option (2) open to them again, and could bid $20 to have their pending ban annulled, and nominate a new bannee (not the orginal person they nominated though)
It was hilarious and raised a lot of money, and would work well here.