Dead Rising 2 has multiplayer, up to 6000 zombies on screen

[TheSteve]

If I remember right, you could throw a propane tank down into the ones outside. They were "real".

That said, 6000 being rendered in any given area is necesarry if this is really going to be multiplayer-- maybe not couch side co-op, but actual multiplayer-- as people coudl be running around all over, and you don't want zombie pop-up.