Scrolling through amptoons wonderful blog (the link is down on the left), I came across a list of Joss Whedon's ten favourite episodes.
I'm not yet enough of a Buffy nerd to remember every single episode, but most of those listed were indeed wonderful, especially 'Hush', 'The Body' and 'Doppelgangland'. And I really liked those episodes in which Buffy and Spike get together in that strange, masochistic way. Maybe I just like to see imperfection in people. Maybe it was refreshing for a white, middle-class, nice girl display signs of serious disturbance.