The whole film world is held together with gaffer tape: everything from taping up small lights in hard to reach crannies & nooks, to putting a mic up the leading man's pants leg, to masking stray light off a lens.
At a recent birthday party, a gag gift was a natty second-hand sport coat entirely covered, tastefully, in silver duct tape. It was probably water and fire proof !!
A stage techie for a big summer concert told me that the huge stacked speakers were held together by 3-foot long strips of gaffer tape rolled in a tube and X'd to the sides of the speakers. He said it took three strong guys to pull the speakers apart after the show.