- Ned getting his head chopped off.
- Purple wedding
- the confirmation of R+L=J
- Sansa, Davos and Jon going to Lyanna Mormount for her troops
- Almost any scene with the Hound in it.

In that it went all downhill from there

Shame
Burning of Stannis' daughter
Dire wolf death with cubs
Pushing Bran out window
Arya cutting the candle to fight in the dark

Really, three, I guess:

- Cersei and Sansa scenes
- Cersei and Tommen ("the lion and the wolf and the stag" parable)
- the Hound and Sansa scenes ("your brother was a killer", etc.)

Also, Grenn's stand against Mag the Mighty at the Wall was superb as well.

I watched Blackwater again recently. The difference in the level of writing is so stark that it's tough to believe it's the same show.