Hm... tough one, as I love every episode of TCW. But, if I had to choose, perhaps Cargo Of Doom. I love the attack on Cad Bane's cruiser, and the torturing/killing of Ropal is both gripping and dark. I love Cad Bane's lines in it as well. And that moment when Ahsoka is getting tortured and there's a close up of Anakin's eye opening, sensing through the Force the torment of his Padawan is also very moving. A close second/third would have to be Landing At Point Rain and Legacy Of Terror, both action-packed and we get to see some of the history of Geonosis.