Just that, really!
One that forever sticks in my mind is a few years ago, when I had a full blown hallucination.
DH and I were driving with my sister, back home from collecting a takeaway. Middle of winter on a quiet, tree lined 60mph road. We were all chatting away, nothing huge had happened that day.
Anyway.. all of a sudden, the car in front of us flipped and rolled over and over again, bursting into flames. DH was driving and I didn't think twice.. I grabbed the steering wheel, forcing the car into the oncoming lane. Thank GOD there was no traffic coming the other way. It happened SO clear, right in front of my eyes.
DH and my sister were shaking with fear and rage at me. I fully hallucinated the whole thing. It felt so real, it absolutely terrified me. I ended up researching the road and if any incidents of a similar nature had ever happened there in the past. A week prior, in 1998, the exact event happened. A car burst into a ball of flames, killing all inside 
Needless to say, it still freaks me out to think about.
Have you ever had anything similar happen?