First off, I want to be very clear that I do not want to role play unless the average reply consists of three solid paragraphs. Note that because of the zombies that plague the land, these role plays will not include much romance. In fact, there won't be much sex (if at all). That doesn't mean the entire role play will be emotionless survival. But damn! Could you imagine trying to have sex while there are potential dangers around?!
Now onward with plot ideas.
After a few days of the zombie apocalypse, so many people are dead or turned into zombies. Two young adults happen across each other, whether it be at some store or maybe they even decided to hunker down in the same area. So the idea is that they spend the night close to each other, perhaps locked in some small room together so that they can sleep peacefully without worrying about zombies attacking them. Then, the next morning they go their own ways. Let's imagine that they meet on the East coast. Fast forward months later and perhaps a thousand miles away from where they first met, the two characters meet again. This time they desire to stick together, for the sake of having someone to talk to.
I hate you
In college, these two just don't get along. He's a smart ass and she's a bit of a bookworm. Unfortunately they're both smart and working towards the same degree, so that forces them in many of the same classes. Every time the two happen across each other at some party, everyone knows to keep the two apart. As the drinks flow, their likelihood of fighting grows rapidly. Their fights often quickly turn from angry shouting to blows. She isn't afraid to hit him and he doesn't mind hitting back. What happens when they both choose to hide in the same room the moment the zombies attack? Their struggle to survive is made more difficult as they continuously fight.