I have a use case for a script that requires A's signature and either B or C's. I've created a $50 bounty, payable in BTC, for this at Bountify.co.

My use case is to allow mediators to be paid via a second address for a transaction so that the mediator is A and the buyer and seller are B and C. Even if this doesn't end up being used for this purpose there is obviously great utility in being able to build more complex redeem scripts.