Not entirely a 'car accident' but I was driving down the interstate and narrowly dodged a shovel head (the handle had broken off) sitting in the far left passing lane in a construction zone. The car behind me hit it and I watched in my rear view mirror as it flew up in the air and traveled all the way over to the right side travel lane and fucking demolished the windshield of a car. I was expecting the car to jerk and swerve from the driver freaking out from this object falling out of the sky right into their windshield, but they just very calmly merged to the shoulder and stopped.

The other one was me barely missing an empty pallet sitting in the middle of my lane when it was dark out and seeing the headlights of the car tailgating behind me do a complete 360 as they tried to dodge it. If they'd left a little more room between us they probably could have followed my lead and drove around in, but their short following distance left no time for them to react.