Think about it. Your buddy is kiting the **** out of a crowd of zeds, about to run through a doorway, and then *creak* *slam* and over microphone "Gotcha *****!"
-Joker
LOL, where do you people get these ideas from??
It'd be nice for griefing.
Indeed. I can imagine it to be rather horrible on pub servers with people closing doors in front of the survivors just to piss them off. Or like in some servers, you can join in as spectator even when the server is full, I wouldnt be surprised if most people tried to get the survivors killed so they would leave the server and he could join the game.
Fun stuff like that.
Lol, I suddenly remember Zombie master.
I actually had the exact same idea in mind. This could be used by mappers to create Zombie Master styled maps O_O. One person goes spec - therefor being the Zombie Master - and he could control doors and other triggers in the map trying to kill the players. The triggers should be placed somewhere where players cant reach them or if possible make them spectator triggeable only in the first place.
So basically a mapper would create a map full of these triggers in mission map style so players are forced to move, and then see how long the players survive. But it might require some pretty complex coding to make it work the way it does in Zombie Master, if you wanted to include the resource system and everything which are required to trigger the traps. Otherwise it would be just triggering traps one after another without any limitations which could be a tad pointless.
EDIT: Oh and I suppose you could simply use an invisible player with the ghost cheat active instead of spectator mode, if its easier. The Specimen Versus mutator used an invisible player for spawning so something like that could work right?