I felt this was the most emotionally charged episode of the season. From Robb executing Karstark to Shireen rushing to meet her father, every scene was really about how people felt in them. I think Arya and Shireen also carried this episode, though Tywin at the end as always swooped in for the best work of any character.
The hatred on Tywin's face when he said he recalled Tyrion's marriage was perfect, as was Cersei's plea not to be sold off again. In the end, it was just a good series of twists and plots.
Question of the Week
Did Robb have any option other than the one he chose in executing Rickard Karstark?