Dark of the Alley

Sherlock with an especially 'King of the Assholes' kind of attitude at a crime scene. John keeping quiet until they're out of sight, then he shoves Sherlock up against the wall of an alley, or into a shuttered alcove, and telling him in quiet, explicit tones exactly how Sherlock will make it up to him. More intimate than any flagrant public indecency. Then John just walks away.