Deadlands: Shadows in the West
Pulp novels describe your basic walkin' dead as slow and mindless. Obviously the writers have never truly encountered them. Creatures like these aren't the kind to shuffle about like they hadn't a thought in their rotting heads.
These suckers are mean and clever. They know people think they're supposed to be slow and stupid, so sometimes they act that way just to get close. And by the way, they do feed on brains. Delicious, succulent brains.
In the Huntwick mines the group encountered Dr. Ognen's experiments. These seemed to be oblivious to everything around them that didn't pertain to their tasks. They followed strict orders and nothing else.