Hannibal & Will Graham (omg Will's "I wanted ice cream" face is so sadly adorable!)<<Will not appreciating the high-caliber cooking Hannibal makes him is outright hilarious, especially when you know that there's almost definitely people in it.
In "A Scandal in Belgravia" Sherlock calls Lestrade to tell him that there's been a break-in at Baker Street. Sherlock tossed the American out the window, repeatedly. Lestrade would have had to explain it without implicating Sherlock in a crime.
Another sad headcanon? At some point John is going to get severally injured on a case and probably almost die and we're going to get to see heart broken-murderous Sherlock << go ahead, rip my heart out.