Doubtless this is my sleeping brain messing with me, but I seem to have had a dream that Harry would go on some sort of training course/vision quest in which his patronis would instruct him to cast the killing curse. Except this is somewhere in Hogwarts (probably the second floor?), and he figures based on the angle of the curse that it's going to hit the great hall... so he runs down in time to see it hit Neville. But on the way to DUmbledore's office with Neville's body, he casts "Accio Neville's Soul", then does something with Patronis 2.0 and Neville wakes up. (Dumbledore's met him on the staircase by that point).

While I don't expect this to be at all like what actually happens, it does make me wonder if anyone's tried "accio soul" before.