While playing on pl_goldrush with storyteller18 tonight, an offensive engineer managed to mess me up pretty badly. He had set up an engineer nest at the entrance to the tunnel connecting the two main areas of the field. He was sitting there, randomly firing the shotgun into the tunnel, hoping for a spy to flicker. Even when I knew he was doing it, waiting for him to reload wasted precious seconds of cloak and left me in a very bad position, since I would be waiting in a frantic combat zone.
It really was a brilliant tactic, one that I will use if I am an engie on offense on pl_goldrush. I had no solid way to counter it, and no alternate paths to get by him. Even if he didn't finish me off after flickering, someone else almost always did.
http://www.visual77.com/2009/05/the-way-of-the-spy-part-3-pl_goldrush/