1. Euphemisms. Silly little expressions like 'passed on' or 'went to a better place'. Everyone knows that what they all mean is 'dead', so why not just say that?
2. The whole notion of personal privacy. If John only hides something under a pile of socks at the back of a locked drawer, he shouldn't be upset in the slightest when Sherlock has come across it within days. Child's play.
3. Small talk. Sherlock is quite content to sit in silence, and actually would rather do that - mind free to wander onto an infinitely more interesting subject, such as what he should write his next monograph upon - than make lame conversation about the weather or whichever team is currently best at kicking a ball around a field.
4. Birthday parties. Why does society consider it such a momentous achievement to have breathed through another year?
5. John's obsessive and ridiculous need for a tidy flat, and his refusal to accept some extremely interesting and potentially useful mould growing on a forgotten loaf of bread as 'clean'. He doesn't really understand why John insists on such cleanliness - perhaps it's to do with him being a doctor - but Sherlock reluctantly complies in order to avoid having to find a new flatmate.
Hello, dearest readers... it's been a while! What do you think of my latest offering? Any suggestions - which I may or may not be inspired by - for future mini-fics?