Some charter Airlines use the 3x3x3 configuration for their airbus A330 and A300 (and possibly the A310). this gives them more capacity, so that they can provide lower fares than scheduled operators. this topic was discussed a week ago. Search the thread.
A300, A319, A320, A321, A332, A333, A343, A346, A388, B734, B738, B744, B772, B773, B788, F70, MD11, CRJ7, CRJ2, Q400