Here's another merging issue that I've run into a couple times recently. I'm pretty sure my actions fall into the "two wrongs don't make a right" category, but I didn't really care much at the time.
On ramp to a highway, going down a hill from an overpass, not much traffic on the two lanes in that direction on the highway. There was someone a couple of cars ahead on the ramp going pretty slow, which is pretty frustrating when you are trying to speed up to highway speed. I figured I'd be able to pass soon enough once we were on the highway, though, so no big deal. The problem was that some guy three cars behind me decided to move early, crossing one solid line and then another (the sides of the curved triangle between the on ramp and the right lane of the highway) and all the way into the left lane in one move. By the time I was on the highway with my signal on to change lanes, he was already coming up pretty fast. Screw him, I changed lanes anyway and got him upset. I'm sure he didn't have to brake, but probably had to take some off the gas. But if I had waited for him, there'd be the chance that I'd then have to wait for everyone else behind me as they changed lanes as well as I got stuck behind the slow moving vehicle.
Anyway, I made the pass quickly, got into the clear right lane and then laughed as the girl in his passenger seat gave me the finger as they passed. Of course, once he was by me, he apparently wasn't in such a hurry anymore because he slowed down to about my speed a bit ahead, staying in the left lane with a few cars right behind him probably cursing at him for not moving over.