Severus and lily.
This is in no way me trying to rewrite what Rowling did, cause it's awesome, I just wanted to write something that showed Severus and Lily getting together. So here is my attempt, hope someone out there likes it. 

He who must not be named stepped over James' body and stalked towards the door, where on the other side Lily Potter was trying to pile items against it. A futile attempt to protect herself and her infant son. She rushed over and put Harry in his crib. Panic stretched across her face, Harry couldn't die, he just couldn't. A flash and a bang and Lily knew He had blown...

After a short time from the battle Harry insisted to go to the head masters office alone. Once he was in the office he went straight to Professor Snape’s portrait.

Harry: "Hello Professor"
Snape: "Oh, Mr. Potter to what do I owe the pleasure of your presence today?"
Harry: "I have brought something I recently found in my vault at Gringotts that was addressed to you."
Snape: "Me? What would possibly be addressed to me in your vault Mr. Potter?"
Harry: "It’s a letter sir, from my mother I recognized the hand writing from a letter I found at Sirius’ place."
Snape: "Okay, Mr. Potter please read...