First of all, each of the "epiphany" scenes were all emotional wallops. I loved each and every one.
Jack's scenes with Desmond: "There's no going back, no do-overs. Believe me, I already tried that. What happened, happened" I'm paraphrasing, but I love that scene. Look at Jack's transformation just from the S5 finale which was all about undoing everything, to that moment. And "See ya in another life, brother" - I love that line and the way they used it here.
Kate to Desmond: "Christian Shepherd? Seriously?"
Flocke to Jack: "So its you? Aren't you the obvious choice?" Great nod to the audience.
Richard starting to age but wanting to live.
Jack and Christian - I *LOVED* that scene. I know some others didn't, but for me it was spot on.