"Ephialtes, may you live forever."
How about the scene where the "god emperor Xerxes" comes to Thermopylae and tells Leonidas that he has done well that day, but that tomorrow, the Persians will unleash their "Immortals." Leonidas replies, "So? From what I've seen, we should have marched our women up here. We'll test your Immortals and see if they live up to their name."
There are too many good lines in that movie to pick only one ...
And of course there's the classic:
Xerxes: "My archers will blot out the sun with their arrows."
Leonidas' captain: "Then we will fight in the shade."
300 is an instant classic that will drive the wuss critics crazy for decades. (like the critics of the time thought Shakespeare was pedestrian junk)