1. Hermione Granger has always found Severus Snape to be incredibly sexy. Now that she's the Arithmacy Professor at Hogwarts, and Ron has run off with Draco Malfoy, she's finally free to seduce the Potions Master and current Headmaster into her bed. Unfortunately, little does she know, her competition is none other than the Defense against the Dark Arts Professor, Harry Potter. (Obviously, Harry wins in the end.........)
[Alternatively, it would be just as awesome to see (Quidditch Star) Ginny Weasley competing with Harry for Severus's affections. xD)
2. Once, deep in the throws of love and passion, Harry and Severus committed themselves to each other and got married. Three years later, amongst misunderstandings, miscommunication, and none too little sabotage, they part ways and divorce. Moving far far away and disguising himself, Severus ends all contact with Harry, while Harry mopes around, both denying the longing they feel for each other. At some point, sick of having to explain himself to everyone in his life, Harry moves away and hides behind glamour and a false identity. Little does he know that the absolutely gorgeous, intelligent, attractive, next door neighbor he's just gained, whom he is seriously considering pursuing, is none other than his ex-husband.