I was working on this for another game before I got kicked from their forums...
http://img233.imageshack.us/my.php?image=backlot4dr3.jpg
http://img233.imageshack.us/my.php?image=backlot2hu0.jpg
http://img246.imageshack.us/my.php?image=backlot1ei4.jpg

The physics/traps/spawns work perfectly, the idea was for (some) to fend off waves of Z's while (others) worked on deciphering the code on a keypad, while still (others) performed various tasks like protecting a generator. The person in charge of the Zombies would have to almost manually open the gate by breaking a func_physbox that barred the gate( this proved to be fun and challenging)...once open it would be up to the players to clear out the zombies and re-bar the gate with various physboxs strewn about, it was never tested on a server, but what I left off with exceeded my (and others) expectations.

This is a mostly Brain Bread forum, why is this map Zombie Master?
I don't have aproblem with this map or that mod but this would at least be the wrong section, if not forums.