Challenging Death. First, Alex literally throws down the gauntlet. Death accepts the challenge, laying out that he has heard every tale that could come from mortal lips, and finishing with "Make me cry." Then, Alexander takes out the Beast's mirror and...
Okay, this one does need some more exposition. Alexander pulls out The Mirror of Truth and declares "If your existence has been all that you say it has, then truth alone shall be my sword!" The Lord of the freaking Dead is forced to watch the only story that could possibly make him cry: his own. He gets to see how he went from mortal man to immortal and essentially soulless monster and all the sadness that he was consciously ignoring. When he can't take anymore, the Mirror of Truth shatters, and he lets out a single tear.
Lord of the Dead: Truth is indeed a terrible thing. I have worn this mantle for so long, I had forgotten its dreadful weight.
The Golden Ending - Awesome Moment of Crowning, everyone shows up to the wedding, the music is just as cheerful and celebratory as it should be, and it ends with Jollo dancing and performing tricks for an appreciative crowd. It's hard not to cheer.
My favorite moment is in this installment as well. Alexander has completely trashed Alhazred's plans, breaking up his sham wedding, exposing him for the corrupt, amoral asshole he is, and chasing him up to the tower where he has Cassima bound. Alex disposes of the genie (either by killing him or taking control of him). Alhazred, finally out of mooks, draws his sword, at which point Alexander grabs a heavy ceremonial sword, and, despite the fact that it's absolutely not a fighting weapon and he's outmatched, he managed to hold off Alhazred for quite a while. Then, when Alexander is just about out of strength, Cassima escapes her bonds and distracts Alhazred by stabbing him in the shoulder, at which point Alexander takes advantage of the distraction to clock Alhazred with the flat of the heavy sword. Even in victory, he spares the life of his enemy. The whole scene is epic awesome as far as I'm concerned.
Also from the Golden Ending, when Alexander tries to stop the wedding and the false Cassima orders his execution, only to be interrupted by Cassima's resurrected parents bursting into the hall.
King Caliphim: Hold, in the name of the true King!