There are five things that drive me so insane with rage, it makes me rather thankful that guns are illegal in this country. I'd probably run amok with a Kalashnikov, otherwise.
Discarding teabags in the sink. Because, by Christ, it's so bloody hard to turn 180 degrees and flip them into the bin instead.
Dawdlers. Completely distinct from flaneurs, who idle creatively and decoratively, dawdlers simply have no sense of purpose. And nor are they capable of dawdling in a straight line, so one can skip past them. I have to summon up all my energy to imagine the ghastliness of a life behind bars as a disincentive for pushing them off the pavement and under the wheels of a passing taxi.
Tourists. Particularly those who pause at the top of the escalator in the underground, gawping hopelessly at their tube map. If I could possibly go undetected, I'd, erm, help them come to a decision about their journey by giving them a hefty push down the stairs.
People who both smoke and are vastly overweight. I'm sorry, but you're only allowed to commit one mortal sin at once. If you want to kill yourself, please do it in a swifter and more attractive fashion.
Grown adults who revert to teenage behaviour once they're in a communal kitchen or bathroom. It's the office - your mum is not going to come and clear up after you.