Three of my favourites...
Someone on a posh bike and wearing graham weigh lycra undertook me in a cycle lane I was also in as I approached a busy set of lights outside Chester. He passed within a couple of inches and made no acknowledgement to his idiocy.
Someone once overtook me in tatton park on a quite breezy day and immediately afterwards blew a mouthful of gob back towards me. He obviously has boundary issues.
The entire club ride of one of the local "wheelers" one Sunday, half of whom overtook me approaching a x roads and then the lot of them called a Left while I was going straight on. Cue those who had flocked to my right and those immediately behind me cutting me up and riding into each other, then giving me dirty looks.
I generally find the bigger the herd or the flashier the lycra, the more arrogant cyclists become. Acceptedly that's a generalisation.