No, I haven't, thank goodness. However, I have narrowly managed to avoid some accidents caused by others' actions and seen some actions that could have led to accidents.
1. On my driving test, in a narrow busy town street, waiting behind a car for the oncoming traffic to stop, so I could overtake. Just as the traffic stopped and I was overtaking, the car driver opened his door right in my path. Luckily, I had seen the door wavering a bit and I was far enough out, that with a bit of extra turn of the wheel, I avoided it. I passed my test.
2. A driver driving far too fast in a 30mph zone didn't see the traffic lights turn red. Children on a crossing had to scatter to avoid his car.
3. A driver unwilling to wait in a queue drove up a lane that was closing in a short distance and pulled in, in front of me, causing me to brake hard to avoid an accident.