Although the worst so far was the delivery driver that neither knocked nor rang but banged on the window of the front room (could see me working there) - I jumped out of my skin!
I hate it when people bang on the window, when there's a perfectly well-known, long-established custom of ringing or knocking at the door to request somebody's attention. It's as if they think they're private detectives (also appropriately known as 'dicks') who want to shame you into knowing that they've caught you red-handed in the act of being inside your own house. If it were somebody who needed to come in to the house (meter reader or whatever), I'd be half-tempted to insist that they have to clamber in through the window rather than use the door which they were clearly unable to find.
It's also scary how many people are driving vans and cars through busy traffic, but do not have adequate eyesight to be able to see a bell and/or signs saying 'out of order', 'please knock' or 'please ring bell'.
We have similar issues with people at the door, delivering things. We have a letter box and a parcel safe on the wall. Just in case it isn't instantly obvious that you use the letter box as a letter box or use the parcel safe instead for items that are too big to fit through the letter box, there are clear instructions on the parcel safe to this effect and telling you how to lock it.
The number of times people put letters in the parcel safe and leave it unlocked is annoying enough, but we still get small parcels just left outside on the step. On a number of occasions, the postman has put a bunch of letters in the parcel safe, left it unlocked, and then immediately knocked on the door with a parcel (not tracked or sign-for) that could very easily have gone in with the letters.
The most baffling are the delivery people who see the parcel safe, follow the instructions and manage to lock it, but don't think to put the parcel in first - or don't have a parcel in the first place, but had such an easy schedule that they had spare time to randomly play with parcel boxes that they didn't actually need. I see it locked, unlock it to get the contents and just find it empty.
I hate to patronise the reasonable amount of people who do understand basic house-visiting procedure, but I often wonder if I should print out an idiot's guide/flow-chart, detailing every single tiny little step they need to follow. Problem is, as we've already read here, the only people who ever would bother/be able to read it would be the ones with basic common sense who didn't need it in the first place.
I'm loving the dingbat recounted upthread who peeled the black tape off the non-functioning doorbell, rang it and, I'm guessing, was utterly bewildered to discover that it didn't actually work! What's the betting that it's the same kind of person who sees a huge 'wet paint' sign and feels the need to smoosh their hand into it to check if it's true or whether the householder simply had nothing better to do than put it up next to the clean, shiny, obviously newly-painted surface for a giggle?!