Lucario was my MVP, Aura Sphere and Shadow Ball were a damn good combo. Honourable mention goes to Cobalion, Sacred Sword and Iron Head were awesome all out assault combos. Metagross was helpful too, Meteor Mash and Iron Defence made him indestructible. (I'm kind of a sucker for combination steel-types).
Dishonourable mention to Virizion and Terrakion for being a major let-down after Cobalion.