What I WANT to happen is zombies, depending on what type of zombies you are talking about.
Are they Shaun of the Dead style Zombies? Since zombies aren't real and there are multiple types of them in different movies/entertainment, I'm going to go with that style, in which case they are slow moving, dumb, easily killable creatures. It would be interesting and dare I say somewhat exciting to survive and live in a world with those type of zombies.
“Anna, my strong, terrifying Anna.” -Cas
"You lack the requisite spine and testicular fortitude to study under me" -Elodin