You wake under a full moon. Whether you are able to see it yet or not, it is there. You find yourself trapped inside a small, claustrophobic box. It may have linen padding inside, it may not, depending on how things were arranged for your funeral. Finding yourself buried six feet underground in a coffin may shock you, but somehow you manage to break out and dig your way back to the surface. Maybe you needed to rest in between digging, maybe not. But getting enough oxygen down there is no longer an issue, for you do not need to breathe to live. Or maybe you did not dig your way out, perhaps one of your fellow undead helped you out of that grave. Or maybe you were not even buried at all after you died; perhaps your body was unceremoniously thrown into the woods to become food for the wolves. Perhaps you were even cremated after death, but whatever the cause you are now alive and well.
Well, sort of. You may look somewhat differently than you did the day of your death; perhaps younger, perhaps older. Perhaps your mind and personality have changed, or even been transformed completely. Your flesh may be pale, if not grey from a little decay. Or worse, depending on how long ago you had died. You also begin to feel cravings for meat, raw or not. New alien instincts from within are telling you to feed. Your body is constantly decaying, and you need to feed from the living in order to delay that process. Although on the other hand, eating a large enough amount of flesh can cause your body to regenerate some of what was lost.
And you are not the only one. Everywhere, the dead now walk the earth. Some of the zombies have all of their memories, others only retain some of them. Some have no memory at all. Some, unfortunately, are brought back mindless; having little to no sense of reason and knowing only to feed. But the least fortunate, however, are the ones that not only feel pain, but are constantly feeling the pain of their own bodies being rotted away.
However some zombies are more fortunate. They will not even smell bad if they eat enough flesh, and may even be able to blend with a crowd of the living. Some zombies are resistant to pain, or are unable to feel any pain at all. Some of them may have slower rates of decay, meaning they require less flesh to maintain themselves. Some zombies are even resurrected with an extra boost to their stamina, strength, speed, or even intelligence. Some of them are gifted with other abilities, like being able to levitate themselves over the ground, have heightened senses, or a sixth sense that allows them to detect the living or other undead. Some but not all zombies can turn other living people into zombies as well, after killing them with a bite. Some of those zombies can even control the ones they convert as minions of their own.
However, such beneficial factors are not common among the undead.
While this sudden unlife you possess itself is a mystery, there are also the living to deal with. People run away from you screaming, some even search for weapons to kill you with -Not that they can. But while you cannot die, your body can still be destroyed and you can lose consciousness forever once your brain is destroyed.
Being able to play as a zombie in an apocalypse of your own is an idea I came up with, but I would rather have someone else take the role of GM here. I have not worked out the settings, plot, or anything other details for the rp, so all of that is free to be created by whoever wants to. Whether you want this casual, free or advanced is entirely up to the gm, and so are the rules, character sheets, etc.