Scary: Taking shelter in a creepy old building at night while zombies prowl the streets outside.
Scarier: Venturing out into the zombie-infested streets in search of a fast-food restaurant that's still open at this time of night. (No, I don't know why that seemed so important.)
Scariest: Driving a van full of survivors in search of a better, more zombie-proof haven... and looking back to see that everything behind you - dirt, trees, pavement, streetlights - has started to crack open, come apart, and get sucked up into the sky. And yes, the destruction is spreading faster than you can drive, but that doesn't matter because this isn't going to stop and there's nowhere safe to drive to.
Zombie dreams aren't all that unusual for me. The world-devouring apocalypse is a new one, though.