I would say, by far.. coming to after losing consciousness from a seizure, and seeing Joe telling me, "Lori I thought you were dead", not knowing where I was, what day it was, what month it was, or even how to talk, and later, finding out that I had turned blue.
Then, in the ride to the hospital, seeing my pulse race up to 144, when it's normally around 70.
Oh, and I didn't even care. I didn't have the capacity. That was scary but not at the time..