In my bochur days, one shabbos a fellow in the dorm left an iron on over shabbos. It was a potential sakanah, and we had no one to ask. We went to a fire department closeby to ask if they would do it, and to tell us if it was in fact dangerous – they laughed us off….so we decided among ourselves to make it a quadruple derabonon. One, unplugging electric appliances is derabonon according to most. Two, it’s melacha sheaina tzricha legufah. Three, we did it with a shinui…and the funniest addition was that we did it “shnayim she’asu” by having one guy put his toe on one side of the plug, and another put his toe on the opposite side, pulling it out together.
Rav Belsky chuckled at our bochurishe “ingenuity”, and said we did fine.