**Wesley Wyndham-Pryce. ** “I’ve prepared for this moment my entire life, and I’m still not ready.”
Caleb “I’m sorry, I didn’t catch that last part on account of her neck snappin’ and all, but did she say that the end is near… or here?”
Sweet, the musical demon.
“I’m the heart of swing, I’m the twist and shout.”
Principal Snyder: “Why couldn’t you have been dealing drugs like normal people?”
Since my favourite vampire (Spike) has already been mentioned, I’ll go with Dracula, to whom Buffy said, “And you’re sure this isn’t a fan boy thing? Cause I’ve fought more than a couple pimply overweight vamps that called themselves Lestat.”
Dawn. “Mom!”
The Fear Demon from the Halloween episode that has them all trapped in the frat house.
Xander (mocking): “Who’s the little fear demon?”
Giles: “**Don’t **taunt the fear demon!”
Xander: “Why? Is it going to hurt me?”
Giles: “No, it’s just. . .tacky.”
jbarro, that would be Gachnar. 
Harmony.
Harmony: Is it safe? Has Buffy gotten to you yet? I saw her patrolling just now… with a stake! She won’t give up until she’s killed me to death.
Spike: Buffy’s looking for you?
Harmony: Of course. That’s why I’m on the lam. Didn’t you hear? I’m totally her arch-nemesis.
Spike: Is that right? I must’ve missed the memo.
Harmony: There was a mem— Spike, oh my God, this is like a real emergency!
The Master: Hold still. You’ve got something in your eye.
The Gentlemen “…”
Willy, the snitch and proprietor of Willy’s Place.
Don’t ever say your friend Willy don’t come through in a pinch.
How about Druscilla, Spike’s original partner in crime?
Hey, I should have thought of starting a thread like this! 
Mutant Enemy’s mascot: “Grr. Argh.”
Halfrek, the vengeance demon.
Tara: I thought vengeance demons only punished men who wronged women.
Halfrek: Oh, that was Anya’s little raison d’etre. Most of us try to be a little more well-rounded. And actually, we prefer “justice demon”, okay? FYI.
Warren, one of the least-effective, yet most hated of the Big Bads.
Warren: Say goodnight, bitch!
Buffy: Goodnight. Bitch.
Clem. ‘I still say it’s weird without kittens.’
Holden, the vampire/psych student: “You do have a superiority complex, and you’ve got an inferiority complex about it. Kudos.”
Kendra Young.
Kendra: In case de curse does not succeed, dis is my lucky stake. I have killed many vampires wit it. I call it Mr. Pointy.
Buffy: You named your stake?
Kendra: Yes.
Buffy: Remind me to get you a stuffed animal.
Mr Trick: There’s a reason these vengeance crusades are out of style. It’s the modern vampire who sees the big picture.