At the end of the film when the first part of the ''Carmina Burana' is playing and the land is blooming because Arthur has drunk of the Grail and relearned that he and the land are one, so he and his knights ride out for one final battle. I choke up every time.
Pretty much the last 10 minutes of the film. Starting with the above mentioned scene it is just straight-up awesome. Merlin coming back as a dream, Merlin's vengeance on Morganna, the battle, Lancelot being a badass one last time, Arthur and Mordred killing each other(including the marvelous line: "come father, let us embrace at last"), and of course Percival throwing Excalibur into the lake and then seeing Arthur being carried away All toped off by that shot of the lady of the lake holding Excalibur with the sun rising in the distant and accompanied by "The Death of Siegfried" from Wagner's Twilight of the Gods = one of the best shot scenes this troper has ever seen in a film and simply pure awesomeness.
Arthur sailing with the three queens into the sunset to that stirring music, whilst Perceval is the sole surviving knight and carrier of the legend and must feel a loneliness incomparable. The viewer is left to wonder when Arthur will ever return to our Mordred-stricken world.
"Nobody shall have the sword! Nobody shall wield Excalibur but MEEEEEEEEE!!!"
Arthur being told by Kay, his beloved adopted brother and Seneschal that Merlin told him in a dream he would fight well in the battle the next day against Mordred. It takes several viewings to realise it,but by the way Arthur and Kay look at each other and embrace, Kay knows he will die the next day. Sends chills down your spine. We never see Kay's fate; he's in the battle at Arthur's side and promptly disappears, but it's obvious what has happened, unless there is a deleted scene of his fate somewhere.
More of an Awesome Moment of Crowning, but young Arthur has knocked down Uryens, one of the knights battling against him. Arthur tries to compel by sword-point to get Uryens to pledge loyalty to him as King, but Uryens refuses to pledge to a lowly squire. Arthur realizes he's right, hands him Excalibur, kneels in the hip-deep water, and requests that Uryens knight him first. Uryens actually stands there staring at the sword that could grant him kingship if he keeps and strikes the defenseless Arthur down (and his fellow rebelling knights are encouraging him to keep it!)... and then he quickly knights Arthur, hands him back Excalibur, and kneels before Arthur accepting him as king.
Even Merlin never saw that coming.
Made even more awesome by the fact that Uryens is visibly trembling as he holds the sword — after he was perfectly calm with it at his neck.
Percival proving himself worthy and gaining the Holy Grail.
"Lancelot with us!" Even the old wound which he still has is overcome by the need to do good for Camelot. The fact that Lancelot probably also died along with Arthur makes it all the more poignant.