The "worst" one I've had was on our maiden voyage in our first motorhome. A truck was passing me on the left and started back into the right lane before he was clear. Luckily, it was on I-10 with a nice wide shoulder so I had plenty of room to move over before he hit me.
The closest miss I've had in a pickup was in 2004. I had a new F-150 4x4 SuperCrew and was driving on a road with ditches on both sides most of the way. This happened in an area with a bike lane. A car pulled out of a driveway on the left. I saw him moving forward and thought he would turn right...he didn't. I was right on top of him when he turned left into my lane. I could see his passenger and he looked like he was about to die. Somehow I got the F-150 into the bike lane without hitting the car or the mailboxes. As I continued home, I looked in my mirror and saw that the car just stopped there. I'm sure the passenger was chewing out the driver.