Dr. Kupferberg revealing at the dinner party that Dr. Melfi was treating Tony Soprano.
Watching Bobby Bacala get his (and knowing his hit was coming as soon as we saw him in the train store without answering his cellphone) was sad but inevitable. Watching Sil and Patsy get hit was another inevitable surprise (the motorcyclist afterwards I think was added to help make the scene more visceral) and watching Tony stare at his door in the safe house, machine gun in hand, just sealed it all up. We knew the House of Soprano was going to fall eventually -- well, it started with Chris' death, didn't it? -- and this episode just hastened the fall.
But still. What got me the most worked up? Dr. K committing a serious breach of ethics and betraying two instances of doctor-patient confidentiality (Melfi/Soprano, Kupferberg/Melfi) ... though honestly, I'm not sure Melfi should've named her patient to Dr. K to begin with. Anyway.
Maybe they'll take the house falling metaphor to a literal extreme next week and Carm's spec house will fall over. (Maybe one side wall will topple over onto Buster Bluth.) Solid as a rock!