Ok, bits that ALWAYS make me cry:
BTVS
When Buffy kills Angel in 'Becoming PT2'
When Buffy yells at Giles "We're not supposed to touch the body!" in 'The Body'
When Spike breaks down at the sight of Buffy's body in 'The Gift'
When Xander tells Dawn that she's not special, but extraordinary in 'Potential'
When Anya dies in 'Chosen'
When Spike dies in 'Chosen'
When the end credits roll in 'Chosen' and the Grr Argh Monster turns to the camera
Angel
When Doyle asks Cordelia if "This is a face you could learn to love" in 'Hero'
Doyle saying to the camera "Is that it? Am I done?" at the end of 'Hero'
When Faith asks Angels to kill her in '5X5'
When the team arrive back from Pylea and find Willow sitting on the couch
When Fred asks Wesley "Why can't I stay?" in 'A Hole in the World'
When Conner tells Angel "I learnt that from my father" in 'Origin'
When Illyria asks Wesley "Would you like me to lie to you?" in 'Not Fade Away'
When Angel says "Let's go to work" in 'Not Fade Away'
Scenes that always make me laugh out loud:
BTVS
When Buffy gets the note that Cordy's been kidnapped, and to come alone or that make her a meal, Xander yells "They're gonna cook her dinner?!" in 'When she was Bad'
When Kendra lets the crossbow fire and Buffy yells "It's ok, Kendra killed the bad lamp" in 'What's my Line PT2'
When the gang all think Willow's a vampire, and she comes to the library, Xander shakes his cross, thinking it's not working, and then they all hug her, even Giles, and Willow asks "Say, you all didn't happen to do a bunch of drugs, did ya?" in 'Dopplegangland'
Anything Spike says in 'Pangs'...or season 4 in general
Anya's Bunny outfit in 'Fear, Itself'
Any time Anya's Buny fear is mentioned
When Spike punches Tara and Willow yells "HEY! OH! HEY!" in 'Family'
Anya and Tara describing the plaque Xander made for Willow in 'Bargaining PT1'
Buffy telling Spike "We do not joke about eating people in this house!" in 'Older and Far Away'
Tara wondering why Spike has a muscle cramp in his pants in 'Older and Far Away'
Buffy asking Riley if he died, and telling him "I'm going to win" in 'As You Were'
Spike's drawing of Angel in 'Chosen'
Angel
Anytime Doyle calls Cordy 'Princes'
Wesley and Angel's dancing in 'She'
The first time we ever see Lorne in 'Judgement'
Angel singing 'Mandy' in 'Judgement'
Cordy screaming at Lorne's decapitated, yet still talking, head
Cordy asking Lorne if she could hit the intruder over the head with him
Everyone but Fred jumping with fright as Lorne's head starts talking
Gunn asking Wesley why people keep putting him in charge of things
When Lorne's friend comes to close the portal to Quor'Toth and she keeps popping in and out of reality, especially when she comes up behind them, and Cordy and Gunn scream
Gunn's "This is so much harder than it looks on Batman" crack in 'Ground State'
Gunn telling Wesley "Oh, your ass better pray I don't look that word up" in 'Spin the Bottle'
Fred repeatedly asking if anyone had any weed in 'Spin the Bottle'
Lorne turning to the camera, even though he was still unconscious, and asking "Can you believe these guys?" while Fred's staring at him in 'Spin the Bottle'
Any scene involving Spike and Angel in season 5
Puppet Angel
When Angel tells the group someone will betray him and Spike immediatly raises his hand. When Angel tells him No, he asks if he can deny him three times in 'Not Fade Away'
Illyria putting her fist through Vail's head in 'Not Fade Away'
There's probably hundreds more, but that's all I can think of right now.