Since I've been listing three moments for each, my second favorite moment would Pippin’s departure from Edoras with Gandalf. I love Merry and Pippin here so much. “Why do you look? Why do you always have to look.” And Pippin's "Merry!" as they ride out of the stable, and the way Aragorn runs after Merry to watch them ride away.
Third favorite moment is Minith Morgul, with the witch king on his fell beast and the exquisite colors of the place. This was particularly awesome on the big screen... it lacks that terrifying grandeur on a television set, but I still wait for this moment, Gollum and Sam trying to haul Frodo to safety, their hiding behind the rocks while an army of orcs emerges and the witch king presides over all. Amazing moment.
As for a favorite line... hm. I don't quote this movie much. I guess Aragorn's "I do not fear death" line.