I don't think one is out there. Realistic zombies are shambling corpses that can be put down with a single shot to the head or a few to the chest. (I know this because zombies are TOTALLY real). That's something that's always bothered me about zombie movies. How do people get caught by these things?
World at War's zombie mode was pretty close to "realistic" for the first few waves, but once the zombies start to swarm, sprint, and take a full magazine to bring down, realism goes out the window and it's time to run.