I'm thinking of:
unnecessary close passes made by dozy/lazy/inattentive/bellend drivers. And I have, on more than one occasion, been pondering buying a 'lollipop' to stick out the side on the seat downtube.
However, a friend, as a recent birthday present, gave me a
https://passpixi.com '. You can either: magnetically position it over one of the rear cycle shirt pockets or, as I do, have it on the back of my small back pack.
Results: I am very very impressed! On a couple of recent 3.5-hour road rides I was given a heck of a lot more 'passing room', not only by the usual
modern-family-saloon-bigger-that-some-vans but, commercial vehicles were incredibly respectful*.
Okay, to be fair, with regard to the hundreds of cars that must surely have passed me, not everyone played the game, but it
really was a significant amount to be noticeable.
*with vehicle drivers, this word is used loosely. It's most likely a recognition that they might appear on YouTube or their company's bosses are made aware of, or possibly –
though don't hold your breath – a visit from the police!