It happened to me a couple times
Honestly, my response depends on the other person's actions, my perceived danger level and my anger level. My first experience up close and personal was when I was leaving a parking lot and I pulled in fromt of another guy leaving. As I stopped for traffic, I see him flip me off, jump out of his car, run up to my driver's side and say "what the @#$%^#$%^&*#$%^&* do you !@W#E$%R^&*( think !@#$%^&8doing. I cracked the window about two inches as he rapped on the glass with a fist and I politely said "I am sorry if I cut you off, I did not mean to." The response was something like "alright, next time I'm kicking your!@#$%. We went our separate ways. No need for gunplay or to escalate the situation. I think sometimes just swallowing your pride and being polite works wonders.
Another time when I was riding my motorcycle, I had a car pull into my lane beside me, actually forcing me into oncoming traffic. I was almost killed. I was furious as I thought it was done on purpose. I did not pull my gun, of course, but I rode up along side the car at the next light and gave the driver an earful. When I saw it was a woman, I stopped mid sentence, she apologized and said she had not seen me. Obviously, I did too at that point and went on my way. I was ready for a fight that day, but thankfully it was a polite lady and not a smartass dude.
One night I was driving downtown and had a car with a couple of unsavory characters pulling along side of me, making gestures and such. They pulled in front of me and hit the brakes. I swerved around them and they gave chase. A few moments later, I decided they very well might kill me with their car, if nothing else as they were weaving in and out of lanes and forcing other traffic over. I took two quick turns, pulled a 180 stepped to the side of the car for cover and drew my gun. They drove right past, apparently never seeing my turns. Problem solved. Thank God. I was sure, I was the little bangers next intended victim and I had resolved not to go out like that.
Bottom line: treat people with respect, keep your own emotions in check, use your manners and get out of the way instead of engaging the idiots and you may never have to make your 15 minutes of fame on the nightly news.
Funon1