(If there's only one, return it to the battlefield.) How much does Event: Shredder's Challenge cost
One under-the-radar deck that could make a splash at Worlds focuses on Keldeo- EX ( Black & WhiteLegendary Treasures, 45/113) and Blastoise ( Black & WhitePlasma Blast, 16/101)
Memory Jar (T1, S, Ext) R&D's own Randy Buehler claimed that his Memory Jar deck could kill on the first turn a full 33% of the time
The PC interface makes deck building more intuitive and efficient
Whispers of the Muse (T1, Ext, S, Block) A favorite in "Turbo Xerox" (a blue deck which used minimal land but a ton of cantrips to thin out the deck), Counter-Phoenix (Shard Phoenix + Forbid) and Tradewind-Awakening (put Awakening on the stack, tap all your lands for mana, untap all your lands), Whispers has what might seem like a hefty price to pay for one card but you get to do it turn after turn after turn