The 3 you mentioned are in my top 10.
The night that Lisa fucked Lewis in Misty place is my #1, since I would never expected that. When I saw Lewis dick in her in the loggia, I did not believe it, though I am looking at a wrong apartment, then realized that it is actually Lisa under him.
The honorable mention is the 1st night that Serena slept with Allan alone, the stupid guy refused to do the vaginal sex with her when she begged for it. I never forgive him for that.