"So Good", definitely. "I kid you not" was simply an interesting cameo that became sort of a cult-phrase (sorry, Matt), but So Good was a metaphor on so many levels (I took it two ways: he's just enjoying the moment, and everything feels 'So good', as well as the revenge metaphor. I don't agree with the sexual conclusion, because as far as I know, MJ and Harry were never involved that heavily... if they were, at that point in time, I'd consider that to be entering Sins Past territory.)
And as many people have said, the line delivery was just spot-on.