As I'm a big marshmallow, I cried an awful lot! Many things that made me cry were already mentioned, but anyway, this is my full list!
BTVS
Season 1
In Prophecy Girl, the 'I'm only 16, Giles, I don't want to die" speech.
Season 2
When she was bad: when Buffy breaks down at the end and breaks the Master bones. I cry every single time at this!
Lie to me: The conversation in the end between Giles and Buffy (B: Does it ever get better? G: What? B: Life. G: What do you want me to say? B: Lie to me. G: quote I never remember.)
Innocence: When Buffy cries in her bed at the end. She just put so much emotion into it that I cry just by thinking about this moment.
Passion: When Giles goes in his bedroom, thinking Jenny made a surprise for him, and he sees her lying in his bed, dead, with the opera music and all. When Giles calls Buffy and Willow and we see their reaction. When Buffy hits Giles and they both cry and Buffy says "I can't do it without you".
I only have eyes for you: When Buffy and Angel are possessed. The things the possession makes them say just fits so much their actual situation.
Becoming part 1: When Kendra gives Buffy Mister Pointy, her lucky stakes, and whe know she will die just after. When Buffy runs in slowmotion and is too late.
Becoming part 2: When we see Willow in the coma. Always tears me up. When Buffy stakes Angel. When she leaves home. The music, the scene, Joyce...Awn.
Season 3:
Anne: Buffy coming back home
Lover's walk: When Cordy says "Xander? Stay away from me."+ the final scene.
Amends: When Angel says to Buffy "This world doesn't want me" and she cries "What about me?"
Helpless: When Buffy says to Giles "You did this to me? Who are you?" and then Cordelia takes her back home
The Prom: When Buffy says something like "Bad is just coming. Now it's just worse." and cries.
Season 4:
The harsh light of day: Seeing Buffy so sad all the episode+ Anya and Buffy and Harmony's walk.
Fear, itself: When Buffy and Joyce have the little talk about being scared of having new relationship because you can get hurt when you open your heart to someone.
Wild at heart: When Willow starts crying and Buffy runs at her and hugs her. When Oz left, and both Willow and Oz were crying.
Who are you? When Fait hits Buffy, screaming "You're disgusting, disgusting!"
Season 5
Family: At the end. One of my only happy cry.
Fool for love: when Spike cries 🙁
Into the woods: when Buffy runs and screams like hell but is too late
Crush: The look at Spike's face when he realizes Buffy changed her lock
The body: the tears appears when Buffy screams "Don't move the body!" till the end of the episode.
Forever: The Buffy/Dawn final scene.
Tough love: When Willow is just too late. And seeing Tara brainsucked is also a teary moment.
Spiral: When the Scoobies start running after Glory and Buffy sits and goes catatonic.
The weight of the world: When Buffy wakes up and cries.
The gift: When Anya saves Xander. When Dawn is being cut. When Tara says to Willow "I got so lost". When Buffy sacrifices herself. Her speech. The Scoobies watching her body. All their expressions are just...you know.
Season 6:
Afterlife: When Buffy tells Spike she was pulled out of Heaven by her friends.
Tabula Rasa: Final scene
Wrecked: When Willow begs Buffy ("Please, Buffy, please, I need help please, please, Buffy, please")
Dead Things: When Buffy burst out crying in Tara's lap.
Hell's Bells: the whole end, from the moment Anya begs Xander not to leave her til the moment d'Hoofryn says she can be a vengance demon again.
Normal again: lost Buffy :/ + when she says goodbye (in the dimension with Joyce and Hank)
Seeing red: The AR, Xander/Buffy speech, Tara's death 🙁🙁🙁 and Willow crying "Tara, baby? Tara?"
Season 7
Selfless: Buffy's speech+ Anya's part+ Halfrek's death
The killer in me: The final Killow scene
Storyteller: When Andrew cries at the end
Dirty girls: Xander. Eye. :/
Empty places: Buffy out.
Touched: Spike's speech (both a sad and a happy cry)
Angel
Season 1:
City of: When we see Cordy being really extremely poor.
Hero: Doyle's death.
Expecting: When Cordy is pregnant and seems desperate.
War zone: When Gunn understands too late that it was the trap and that those who went out, including his sisters were in danger.
To Shanshu in LA: When Cordy's visions don't stop, and she screams of pain.
Season 2:
Kate's dad's death, Darla seeing Angel fighting for her and being scared he dies in the ultimate task of the Trial. Darla sired again.
Season 3:
Darla's sacrifice, Angel trying to kill Weasley screaming "My boy! You took my boy! I'll kill you, I'll kill you!"
I haven't watched season 4 and 5 yet, but as you can see, I'm very emotional when I watch those series!