Joking aside, not much scares me. It just doesn't happen without being beyond horrific. But I'd have to say, in the realm of realism, my mate (I don't have one now, but if I did) saving my life at the immediate cost of their own. Even worse than that would be an electromagnetic pulse on a wavelength and strength that would rip apart the astral body, which is, in itself, an electromagnetic field. Without it, you're alive, yeah. But you no longer have a consciousness.