AU. Time Travel. Snape goes back in time, holding the knowledge of what is to come if he fails. No longer holding a grudge, he seeks to shape Harry into the greatest wizard of all time, starting on the day Hagrid took Harry to Diagon Alley. No Horcruxes.

Let it not be said that being Uzumaki Naruto is anything approaching easy; he has an obligation to the future but a duty to the past, and a time-traveling jutsu that lets him travel between both. OR: Naruto travels between the past and the present, and somehow loses himself in the process.