The moment at the end of "I Will Remember You" with Buffy crying and saying, "No...That's too soon..." Even though I think that that ship sailed long ago, I can still appreciate the sadness of that moment.
The moment in "The Gift" when Spike stares helplessly at Dawn, just before Doc throws him off of the tower.
The end of "Fool For Love," when Spike, after being rejected and humiliated by Buffy only a short time before, sees her crying, sits down beside her (without even trying to either hide or explain the shotgun) and says "Can I Help?" (Which always reminds me of the scene in "Star Trek" "All Our Yesterdays,"where Kirk tells Edith "In about two hundred years, there's a philosopher who will advocate the expression "Can I help," even above "I love you." I've always wondered if the writer of that script was a "Star Trek" fan)
The scene at the end of "Showtime" when Buffy cuts Spike free.
And, of course, at the end of "Chosen" when Spike, despite the agony fo being burned alive, laughs with joy that, not only has he finally been able to redeem his failure at the end of "The Gift" by saving, not only Buffy and Dawn, but the entire world, but even more because Buffy had finally admitted her feelings for him.
But, most of all, the reunion of Buffy and Spike, the tearful kisses, the cheers from the army of young Slayers, Giles actually doing a dance of joy, and Angel and Xander over in the bushes, locked in a passionate embrace while Dracula looks on approvingly, proud that his manservant has finally found true love. (I hacked into Joss' private files. Sorry if I spoiled the finale of Season 9, but I just had to share)