Willow's exchange with her mom was classic.
Willow: "Mom, the last time we had a conversation over three minutes was when you were telling me about the patriarchal bias of the Mr. Rogers Show!"
Mrs. Rosenberg: "Oh, with 'King Friday' lording it over the other puppets."
Willow: "I worship Beelzebub! I do his biddings! See any goats around? No, 'cause I sacrificed 'em!"
Mrs. Rosenberg: "Willow, please..."
Willow: "All bow before Satan!"
Mrs. Rosenberg: "I'm not listening to this!"
Willow: "Prince of Night, I summon you! Come fill me with your black, naughty evil!"
And practically all of Doppelgangland.
Willow: Oh, I used to want to--wait, florist means crazy, right? I never wanted to do that.
Willow: Aren't you sort of naturally buff, Buff? Haha, buff Buff.
Willow: Oh, thanks!
Buffy: What?
Willow: "Old Reliable"? Yeah, great. There's a sexy nickname.
Buffy: Well, I-I didn't mean it as...
Willow: No, it's fine. I'm "Old Reliable."
Xander: She just means, you know, the geyser! You're like a geyser of fun that goes off at regular intervals.
Willow: That's Old Faithful.
Xander: Isn't that the dog that-that the guy had to shoot?
Willow: That's Old Yeller!
Buffy: Xander, I beg you not to help me.
Willow: I'm eating this banana! Lunchtime be damned!
Willow: Yep, that's me. Reliable-dog-geyser person.
Willow: That, that-that wasn't just some temporal fold, that was some weird Hell place. I-I don't think you're telling me everything.
Anya: I swear, I am just trying to find my necklace.
Willow: Well, did you try looking inside the sofa in Hell?!
Vamp Willow: Bored now.
Giles: She was truly the best of all of us.
Xander: She was better than me.
Giles: Much, much better.
Willow: Geez, guys, who died? Oh God, who died?!
Willow: I love you guys, too. Okay, oxygen becoming an issue.
Willow: It's really nice that you guys missed me. Say, you all didn't happen to do a bunch of drugs, did 'ya?
Giles: ...Well, um, something...something, uh, very strange is happening.
Xander: Can you believe the Watcher's Council let this guy go?
Vamp Willow: Well, look at me. I'm all fuzzy.
There are so many more, but I pretty much already put an entire episode, so I'll stop.