This one just came to me and I had to write it before going to bed.
The Half-Blood Prince
Everyone in the Potions classroom was sniggering when Severus walked in. He froze as he saw what they were laughing at. There on the blackboard was a caricature of himself entwined with the many legs of the Giant Squid. Surrounding the drawing were several large red hearts and the words Snivelus ... his love knows no bounds.
His fingers tightened into fists, nails cutting into the palm of his hands as he watched Potter, Black, Lupin and Pettigrew collapse into hysterical laughter. He should have known those four were responsible.
“Calm down everyone.” The Potions Professor swept into the room, saw the drawing and with a huff of disapproval quickly banished it with a flick of his wand. “That’s enough playing. We have work to do.”
Quickly moving to his desk, Severus continued watching the four sniggering Gryffindors for a moment before retrieving his copy of Advanced Potion-Making from his book bag. They would pay for this ... one day they would pay. Then picking up his quill, he began writing a little note in the margin of one of the pages.
Sectumsempra -- For Enemies