Johnny Ringo said:
My all-time favourite episode would have to be EARSHOT.
http://en.wikipedia.org/wiki/Earshot_%28Buffy_the_Vampire_Slayer%29
Just watched this one last night. It was very good indeed, definitely one of the better ones of the season, but my favorite is still probably either the Halloween costume episode, the band candy episode, or the nightmares-become-reality episode.