Amazing Buffyverse Storylines

I stumbled on yet another discussion about which show you like best, Buffy or Angel. For me the question has always been easy. When Angel was good it was amazing, but when it was bad it was terrible. Buffy was always at least good, and sometimes amazing to boot.

This led me to thinking: Which storylines on those shows were actually amazing? Not just good, but amazing?

Here's my list:

Angel the Series:
The Darla arc in season 2
The Wesley-taking-Connor plot

Buffy the Vampire Slayer:
Angel losing his soul
The Dawn-is-the-key plot in season 5
Spike's redemption arc, from Fool for Love to choosing his soul (stuff before and after that was good, but not amazing)
Buffy's depression arc

Both shows:
Faith's redemption arc from This Year's Girl to Sanctuary

So, what are your opinions? What storylines in the Buffyverse - or any other fandoms we might happen to share - are amazing to you?