The most interesting accident that I have been to involved a car trying to exit the highway while going much too fast. The car spun sideways, hit a rail right at the driver's door, split in half from the bottom, flipped, and folded open, ejecting the contents. The largest piece of the driver that I could find, and identify as human, was part of a foot. Everything else was in little chunks. I wasn't there when the accident unit arrived to take measurements, but I would guess that there were parts of her at least 100 yards down the highway. This is not including parts that were dragged by passing cars (she was flung into the roadway).
I have actually seen very few accidents unfold in front of me, which seems sort of odd considering I spend around 9 hours on the road per day. I have, though, responded to some really gory scenes. Seeing the people die has never bothered me, as I have never had to get hands-on. I don't know, however, that I would want to be in the position of the EMTs or trauma nurses.