It would be an even tie I think between the final two, "Shadow Dancing"
and "Z'ha'dum." The two episodes are also linked at the hip, so they're
really more like one unit...not so much a two-parter, but siamese twins,
story-wise. They're both very exciting, move the arc forward hugely, and
though they rely on a lot of backstory, are also good points for folks new
to the show to dive in, because they also *explain* a lot of backstory, so
they can get into it.
They're both just lovely, knockout episodes. And, at times, scary as