I would want to argue that a great quote you could use would be the final quote refering to Piggy in the novel, which comes when Ralph sees that delieverance has at last arrived and that the boys are rescued. Note how Ralph reacts to the sight of the naval officers who have come to take the boys away:
And in the middle of them, with filthy body, matted hair, and unwiped nose, Ralph wept for the end of innocence, the darkness of man's heart, and the fall through the air of the true, wise friend called Piggy.
Note the way that Piggy is described in this important quote. He is a "true, wise friend," whose death exemplified what Ralph has learnt about the "end of innocence" and "the darkness of man's heart." It is clear therefore that he has heroic qualities, in the way that he remained loyal and true to Ralph up until his death, and that his death was heroic in the way that he tried to challenge the mob and reason with them, bringing them to their senses. The way in which he failed of course symbolises the triumph of savagery over reason.