Salahadin: Nothing. (turns to walk away, looks back, and smiles in triumph) Everything.
Making the scene even more awesome is the conversation before that, when Salahadin promised that he would give safe passage to every Christian citizen of Jerusalem.
Balian: When the Christians took this city, they butchered every Muslim living within these walls.
Salahadin: I am not those men. I am Salahadin. Salahadin.
His emphasis on his name plays into this through a Bilingual Bonus. Salah a-din is actually a nickname meaning "Righteousness of the Faith". He sets himself apart from the Christians who first took Jerusalem by claiming his righteousness is because his faith tells him to be, not by virtue of it.
The king, Baldwin IV: "I am Jerusalem. And you, Reynauld, will give me the kiss of peace."
Context makes this more of a brutal rebuke and thus more awesome: Baldwin is a leper since his youth; the hand he demands the villain kisses is covered with bleeding sores.
Made even more awesome that he beats the snot out of Reynauld afterwards, even though it pushes his body too far.
His successor, Guy de Lusignan, gets one too: "I am Jerusalem. Assemble the army!"
Except that Guy sounds pathetic and flaccid when he says it, despite being drunk with power. When Baldwin says it the first time, he does so with the strength and confidence of a king who is worthy of his position. Despite being a weak and dying leper, Baldwin's strength of character makes Guy sound like an angry child.
Rise a Knight! Especially the moment when the Bishop of Jerusalem asks, "Does making a man a knight make him a better fighter?" and Balian looks around at the renewed sense of purpose and confidence in the men around him, turns, and says simply, "Yes."
When Salahadin walks around the city of Jerusalem, he stops when he sees a Christian cross which has been knocked to the floor during the siege. He picks it up and respectfully places it back on the altar. According to some news reports, at this scene Arab movie-goers in Beirut rose and applauded.
The final sequence with Salahadin, after his victory. He walks on rose-petals into the Dome of the Rock as Crusader banners fall from the ceiling. His servants and soldiers all bow and turn to leave, leaving him alone. Salahadin bows in prayer as the doors close behind him.
From the extended edition - the Balian vs Guy duel ends with a classic Sword over Head. Guy, injured and on his knees, demands a finishing blow. Instead...
Balian: When you rise again - if you rise - rise a knight.
"SIIILLLEEEEEEENNNNCE!" Because Tiberius can be a badass without ever pulling out his sword.
Saladin slashing Jerk Ass Reynauld's throat after taking a cup of water meant for Guy.
"A king does not kill a king. Were you not close enough to a great king, to learn by his example?"
The entire siege of Jerusalem at the end. The city's badly outnumbered defenders hold off the Saracens for three days thanks to Balian's strategy and the morale boost given by knighting every soldier within the walls.
Saladin shutting down the annoyed mullah who comes to him demanding to know why he did not attack Kerak.
Mullah: (after demanding to know why Saladin has retreated from a fight) If you think that way, you will not be king for long.
Saladin's Badass Boast also carries with it a very palpable Real Life subtext. Upon Saladin's death, the previously-united and enlightened nations under Islam quickly devolved into infighting and squabbling which made them easy prey for the Mamluks. In addition, Saladin's death sowed the seeds of the fundamentalist takeover that has kept the greater part of the Middle East stuck in the seventh century in terms of cultural values.
He carries the theme of the above further before the famous "Nothing, everything" line. When Balian threatens to burn Jerusalem to the ground, including all the holy places of all faiths - "everything that drives men mad", Saladin has a thoughtful moment on the cause of the fighting.
Saladin: "I wonder if it would not be better if you did."
In the fight between Godfrey's men and the Sheriff's forces the German Knight goes down pretty quickly with an arrow to the throat. This doesn't stop him. He gets back up and proceeds slaughter a few of the Sheriff's men before another two arrows send him to the ground.
The arrival of the Crusader army at Kerak, with the Cross appearing on the horizon, followed by thousands of men with Baldwin himself at their front.