Sure, this is always a fun topic to vent.
I work as a bike courier in a mid-sized (700 thousand) North American city. Every day is a lesson in how close you can come to being hit by a car. Most near-misses, for me at least, involve a car going the opposite way to me turning left while I'm going straight through the same intersection (I guess for brits and aussies it'd be right handed turns that would cause this)... for some reason, they assume that people on bikes don't go faster than 10kph and think they can pull off a turn when I'm 10m from the intersection. This happens every day.
My favorite single instance was some 18 months ago when I was on a major street and a van behind me honked (presumably simply because I was on the road), squealed his tires in acceleration and passed me with less than a foot of room. In these situations, I like to stick out my fist and knock on the side of their car as they pass - makes quite a startling noise inside, and maybe makes them realize that they're a bit close if they were just being ignorant.
This fella apparently didn't like that, and screeched to a halt (on this busy street) - as I pulled up next to his window, he's already rolled it down, and spittle is forming around his raging, gap-toothed mouth. He yells 'you smack my car again, I beat the living f**k out of you!!' I'm not a confrontational guy, and I clearly saw I was not going to reason with him, or convince him that maybe he should be a little more safe. I also don't care too much about antagonizing people and getting the last word. My immediate reaction was to say 'alright man, I totally won't do that then'. He stopped, blinked, and continued 'I said, you smack my car again I beat the living f**k out of you - d'you hear me??' To which I replied 'yeah dude, I hear you loud and clear, I definitely won't be doing that', while giving him the thumbs up as extra reinforcement that I wouldn't be smacking his car. He looked perplexed, looked from me to the road for a second and a half, and peeled away - and then drove 25km/h staring at me in his rearview for a few minutes while people honked at him for holding up traffic, until I just crossed the road and rode through a parking lot to a side street that I was delivering to.
It's sometimes frustrating how people can be so caught up in their own anger and self-righteousness that they don't understand that their recklessness can actually have deadly consequences. Stupid stupid people.