Not sure if these have been mentioned before, but here goes anyways. Also, the Dru scene from my banner (just in case I switched my banner by the time you read this, also the Spike scene from my other banner)
1. Doppelgangland - The entire scene in the library when everyone thinks Willow is dead, and then she comes in. Especially Xander shaking the cross to see if it's out of batteries, and one of the greatest Willow lines ever: "say, you all didn't happen to do a whole bunch of drugs, did ya?" Love it.
2. The Zeppo - Every scene with Xander and Cordy is great in this episode. Also, the beginning, when Willow says "the shaking is just a side effect of the fear."
3. Potential - Xander's speech to Dawn. I don't think that one needs any more explaining.
4. Innocence - God, there's just too many. I could probably make a whole list just for this episode. Okay, Giles' speech to Buffy in the car at the end of the episode. Oz's "willow-kissage" speech. Xander being awesome at the army base. The Buffy-Angelus scene, especially Angelus saying "love ya too" as he's leaving.
5. The Body - I love this episode so much that I force myself to re-watch it. Every scene is perfect, but specifically when Xander is saying that he needs someone to blame, and Willow says "Okay, you and me, let's go." (I'm paraphrasing)
6. School Hard - The best Spike line ever: Who do you kill for fun around here? I must have watched that scene a hundred times.
7. OMWF - The Walk Through Fire montage is unbelievable. I watch it on youtube all the time, to the point I'm not sure I can tell which one is mirrored anymore...
From Angel...
1. She - The scene where Angel dances. I would give my left arm to have them re-make that scene in Bones.
2. Can't remember 😛 - Wesley makes Angel wear the pink helmet
3. Darla - The scene where Darla asks Angel to turn her.
4. First Impressions - The Denzel conversation is awesome.
5. The Girl in Question - Angel's cookie dough rant. I laugh every time.
6. Smile Time - Aww, Angel, you're cute!
7. Epiphany - Angel's speech to Kate, with one of my favorite lines from any TV show, "If nothing we do matters, then all that matters is what we do."
8. Double or Nothing - You know how some things are so terrible that they're great? Well, that's pretty much how I see the 'climax' of this episode. Angel: "A three?!"
9. Judgment - Couldn't end it on that note. Speaking of which, the credits during this episode remind me why I love DB so much. "What's everyone doing in my living room?"
There's probably more, but I'm tired.