OK, somebody's gotta be the uberromantic sap:
Doyle kisses Cordy.
Fred dies in Wesley's arms.
Gunn stakes his sister.
Wesley shoots his father. Again and again.
And ok, Angel's in this one, but not the focus -- The moment at the end of S3, when the camera focuses on Willow about to tell everyone that Buffy is dead.
Wesley shoots his father. Again and again.
Ooh yeah.
The brilliant choreography of the Fred singing-Lorne reading-Fred spitting up blood.
Also, pretty much any instant where Lorne reads someone to some importance (Wesley's humming before stealing Connor, Holtz's lullaby before blowing up Caritas).
Lindsey's evil hand speech.
And God help me, I kinda like Gunn and Fred's diner breakfasts.
The look of horror on Lorne's face as Fred sings, as he realizes what's happening.
People beat me to almost all of mine! But I have to add Willow's "I have a girlfriend!", in addition to Wes shooting Dad, Wes and Fred in 'A Hole in the World", and the MoG's "We Are the Champions".
The Man on Fire chasing Fred.
Fred's mom smooshin' the demon with the bus.