The dumbest accident I ever had happened as I was driving home. I was in my old Celica (it was a speedy little manual, loved it). I was into the winding, twisty roads of the development, when I see some kind of little Ford hatch slow down in front of me. It was about 200 feet up, but then it stopped. I slowed down. It put on it's reverse lights. I stopped, puzzled. It started backing up. I honked, but it was pretty far away, still 150 feet. But, wait, it was still backing up, faster now! As it got closer, I started honking hard, couldn't back up, some idiot was behind me. By now, I'm standing on the horn, and it's still backing, about 20 feet. Then it hits me.
Two teenage girls get out, looking shocked. I got out, yelling at them (I am a mom, so I am well-versed in yelling at teens). They just looked sadly at their mangled car. My car, at a stop, had pushed half their trunk in. My bumper had a small scratch. I let them go, since I figured their parents would pick up where I left off with the yelling.
So, yeah, they backed up 150 feet to hit me.

I suspect they NOW understand "objects in mirror are closer than they appear".
What's the dumbest accident you've ever had?