Postmodern ironic horror lit is going through something of a Zombie Renaissance right now. I'm going to come right out and admit I find it mystifying. I don't find zombies compelling. I never have. Now, part of it is that I'm not a big horror fan, whether it's horror movies or horror lit. But even so, there are horror tropes I find far more compelling than zombies. Vampires, for instance. I am not and likely never will be a fan of Anne Rice or Stephanie Meyer, but it seems like there's a lot more to vampires than zombies. Same goes for werewolves, things that crawl out of meteorites, and Lovecraftian horrors. They all seem like they have more storytelling possibilities than corpses that stagger about at one mile an hour looking for tasty gray matter to eat.
That said, there is one specific sub-genre of zombie stories that I find compelling: zombies who have died, been zombified, but somehow keep their wits about them, know they're zombies, and are the same person they were before zombification. And they still have free will. I guess it's because it somehow speaks to my fear of being struck down in my prime by a terminal illness or a terrible physical disability. But I'm sure most people have the same fear, and yet the self-aware zombie with free will doesn't seem to be a terribly common zombie trope. TV Tropes has no mention of this particular subclass of zombie, although they go into a respectable amount of detail on zombie classification.
As I've mentioned, I'm not all that into horror, but I've got some knowledge of the genre through my addiction to podcast fiction. Here are the instances of sentient, self-aware zombies that I've come across:
My Friend Is a Lesbian Zombie by Eugie Foster, on Escape Pod. I love that title. It's been a long time since I listened, so I'm blanking on the details, but I remember the title character is realistically freaked out to find she's a zombie (instead of being all blase about it) and if I remember right, they get a happy ending by pumping her full of antifreeze.
The Skull-Faced Boy by David Barr Kirtley, on Pseudopod. A horde of zombies is organizing themselves into battle formation to march on the living, and the viewpoint character is freaked out. Even though he's also a zombie.
American Nightmare by Lilah Wild, on Well Told Tales. As the Zombie Uprising commences, a high schooler freshly killed in an accident gets revenge on those who wronged her. Then she seeks out her still-living best friend, who kills her (for good). This is treated as a semi-happy ending: If she was fated to be killed, at least it was by her best friend.
And finally, in the realm of novel-length fiction, Neil Gaiman's American Gods has a major character who is clearly an intelligent, self-aware zombie, although the actual "Z" word is only used once, for ironic effect. The protagonist's wife Laura, after losing her life in an undignified manner, dedicates her undead days to crisscrossing the country killing bad guys who stand in her widower's way.
No matter how happy they might have been while alive, once they're zombies it's usually taken for granted that they're better off dead (and not moving). Two of the four examples above ended with the zombie character being permanently rendered an unfeeling, unmoving corpse, and in the context of the stories it's accepted as a Good Thing.
And of course, once you're a zombie, there's no going back to being a living human. At one point in American Gods, Laura drinks a potion that restores her, but all it does is revert her to pristine zombie condition; afterwards her decomposition starts all over again just like before.
That's why I find the idea of intelligent zombies who know who they are to be so wonderfully horrifying. How come we don't see more of them in fiction?