I am quite taken with Game Of Thrones in general, but I really love Arya and her sword instructor Syrio Forel. I am no expert on this kind of fighting, but the choreography here looks very well executed to me. I also love how he uses an opponent's cape against him, and all the while he seems very balanced, watchful and calm.
Syrio is brilliantly played by sword master and instructor Miltos Yerolemou.
I also notice as Arya runs away, we hear the fight ensue, but a metal sword clangs to the stone floor. I hope this means Syrio will appear again.