While cleaning/moving our offices around (all our desks at Valve are on wheels so we can have desk races), we discovered this old, long ago used Zombie decision making tree. It was created before our session with Mike Patton to record the common zombie sounds. While it is near indecipherable gibberish thanks to bad penmanship, it shows not at an AI level how a zombie behaves but all the speech opportunities and transitions.
Our favorite is the top. Lay Down? Nope. Want to vomit? Sure.