This is a great question. There are many good quotations that you can choose. Sophocles is one of the greatest playwright in the history of the Western canon. With that said, let me give you a few points on using quotations. First, just because something sounds great, resist the temptation to use it. Only use a quotation if it furthers your argument. If a great quote does not further your argument, it will take away from your paper. Second, try to look for a pithy quote. Often times, short and insightful quotations are the most powerful. In light of these points, I will offer a few of my favorite in the play. I hope that these help you get a sense of the work and the brilliance of it.
Death? "She deserve a glowing crown of gold." (782)
"It is no disgrace for a man, even a wise man, to learn many things and not to be too rigid." (795)
"I see my father offending justice." (832)
"Then she will die, but her death will kill another." (838)