Situational. If someone gets in front of me and I have to change my speed (slow down) or trajectory, that's being cut off. I typically get over, get around them, then get back in front of them. I do it smoothly but make it obvious that they were wrong for cutting me off. No wild gesticulating or screaming. Flashing your lights, honking your horn or even getting animated is going to tip them off that you're going to get back in front. Other things like drifting out of your lane or sitting at a green light, both because of using your phone, get a quick honk. If I see @Roscoe Arbuckle I make sure to zoom in front of him when he's in a line. Again, you have to be subtle and smooth when you do it and juke in at the last minute. Make sure you roll down your window and wave at him to let him know how much you appreciate it.