In some way, I feel bad for Snape. He lost everything and everyone he loved, and even when he would try to make things right, people would still loathe him. Snape was like every house morphed into one person. He was quick-witted in desperate times, he was brave in the face of danger, he was loyal to Lily, and, most of all, he was ambitious to prove himself to those he loved the most: his family, friends, and Lily. J. K. Rowling said that the real reason Voldemort was vanquished trying to kill Harry was partially Lily's sacrifice, but also a vow that Snape had taken with Voldemort not to kill Lily. Sure he could kill James, but not Lily. But when Voldemort killed her, when he tried to kill Harry, the vow came back to him, and he was defeated, for that time at least.
I love Luna. She's absolutely amazing, and she's so kind. She never judges you for who your parents are or where you came from, but she wants to be friends with you. I liked in the Deathly Hallows, Harry was heading up to the tower alone, not listening to what his friends said about it until Luna spoke up. He was very surprised and even a little afraid of her at that moment.