Evil Willow episode really is the episode of all time. The whole episode was just gold from start to finish, but some of my personal favorites were:
Giles: She really was the best of all of us
Willow walks in: Hey who died?
Willow: Oh my god who died
Xander: *brandishes cross at Willow*
Xander: *shakes cross* *brandishes cross again*
SCOOBY GROUP HUG!!!!!!!!! ALSO GILES HUGGING WILLOW!!!!!!!!!
Angel: Buffy...Willow's dead
Angel: Oh hey Willow *turns back to Buffy*
Giles, Willow, Buffy, and Xander: *waiting*
Angel: *slowly turns back to Willow*
"I'm 1,112 just give me a friggin beer!"
Willow: I can't believe this is what I'm like as a vampire! I'm so skanky and evil and... kinda gay!
Buffy, talking about the "evil" thing: Remember Willow, who you were as a person has nothing to do with how you end up as a vampire.
Angel, thinking she's talking about the "gay" thing: Well actually...
Willow: Well could a human do this? *screams*
Anya: Um yeah actually. I'm pretty sure humans do that all the time.
Wesley Wyndam Pryce. Just everything about him
Rip Doppelgangland. No one will ever do it like you I fear.