I forgot to add the finale to season five.
Best Buffy episode
"The Body." My favorite moment is when Dawn's friend, in the art class, turns to her, and asks, "What's negative space?" and she replies, "I don't know." And then Buffy shows up to call her out of the class and tell her the bad news. We don't hear what they say. We see them through the window, from the perspective of the onlookers. The entire episode is about negative space, and is just brilliant. Not much dialogue or music, and beautifully shot.
I'd have to say that is the best one.
Then why are you having drinks with him?! Don't toy with my emotions Revol!!!!!
stop that! don't you know feelings of jealousy and possesiveness will not exist under communism! 
actually some peoples idea of communism is the most soulless shite i could imagine, a dull, rational world of no extremes.
looks like I've missed one or two from season 4 as well. Might have to get the season 4 box set at some point (I got season 3 for 15e (£10 $5)
unless anyone knows of a decent torrent/stream
I've got a coupla invites to bitmetv.org if you want - they've got torrents of dvdrips of all seasons of Buffy including the extras - PM me if anyone wants an invite... you gotta keep a good ratio tho or I'll get in the shit too...

xTx
I agree with j.rogue absolutely - Hush, The Body and Once More With Feeling - but I wouldn't be able to put them in any order, each of those three is so different. All, unsurprisingly, written by Joss Whedon himself. My partner and I have seen The Body twice, I think, and we both cried both times.
And Hush is both the funniest and the scariest episode; and the rudest, I think.
1. The Body - but I can never watch it again, too traumatizing
2. Hush - fucking scares the shit out of me still
3. Once More With Feeling - hilarious, with bad dancing and all. They do a sing-a-long at a theatre here sometimes
I can't believe you spelled it "theatre." You've been hanging out here too much, Rogue!
BTW, I am appalled to discover I now live in "Centre" County. Next I'll be concerned with the flavour of my food.
which is the one in which one of Willow's spells goes haywire and they all forget who they are? The whole lot of them screaming when they see their first vampire is priceless.
Tabula Rasa. That episode rules; I love the part where Spike (or "Tandy Giles") figures out he is british.
I refrained from quoting. It was hard.




So hard to choose.
I'd say The Wish
These are all good too
The Zeppo
Ted
Bewitched, Bothered, and Bewildered
Graduation Day
The puppet show - maybe
Lies My Parents Told Me
looks like I've missed one or two from season 4 as well. Might have to get the season 4 box set at some point (I got season 3 for 15e (£10 $5)
unless anyone knows of a decent torrent/stream