For me...it's a tie between Diego Forlan & Sami Khedira
Forlan still gets nowhere near the credit or recognition he deserves. Mostly based on the below par time he spent at Man United. He get written off as a shithong. But Forlan is a serious player and he has shown that he belongs right up there with the best in the game right now, essentially taking this Uruguay team on his back. I'm so happy for him that's he's shining on this the biggest of stages.
Khedira has seamlessly slotted into the Michael Ballack role with Germany and seriously.....there is an argument that instad of Germany heaping abuse on Kevin Prince Boateng for injuring Ballack causing him to miss the World Cup, they should be thanking him. Because the possibility is great that Ballack, based on his form with Chelsea the past 2 seasons may not have been as effective as Khedira has been on this team. A real compliment to the young man.
The other player who was a pleasant surprise to me has been Schweisteiger. I thought he went missing the first 2 Germany games but in the games against England and Argentina, he's been the driving force of the German team. Schweinsteiger literally ran through the Argentinian defence with impunity. It's nice to see such a talented player mature on the big stage.
I read somewhere where someone said that Maradona concentrated so much on Ozil that he put Mascherano to man mark him, which was mainly effective because Ozil had a fairly quiet game, despite the wonderful pass for the 4th goal. But the fact that Maradona surrounded Mascherano with De Maria, Maxi Rodriguez, and Messi, essentially offensive players, that it left Schweinsteiger the freedom of Cape Town to do as he pleased. He practically destroyed Argentina.