The Handyman's Secret Weapon
A commercial firm has named its product Duck Tape, hearkening back to the original name for this adhesive tape (which was green), developed by Johnson & Johnson during World War II to waterproof ammunition cases.
It is now usually called duct tape, for its supposed use in connecting ventilation and other ducts (which match its current silver color).
Note that modern building codes consider duct tape unsafe for sealing ducts, particularly those that convey hot air.
Okay, it may be unsafe for sealing ducts, but duct tape is an amazing substance and I always keep a roll handy. When traveling in an airport in a third-world country, I keep a roll in my backpack to use as soon as I see my luggage emerging, because it is invariably damaged in some way, sometimes beyond reasonable usefulness. I was toting a big Sterilite container full of baby formula for an orphanage once, and when I saw it being handled off the plane, I knew it was a goner. Sure enough, it was barely holding together and wouldn't make it out of the airport without spilling all the contents. I had my roll of duct tape in hand, however, and quickly taped it up enough to get it out the door and into the truck waiting for me.
It's also been handy for emergency hemming (if the fabric isn't too thin). I have a nice microfiber zip jacket that looks spiffy and professional -- until you look at the inside of the zipper placket and see that it had been duct-taped to prevent it from unfolding. I had had to do that in a backstage emergency, and later I inadvertently let it go through the wash/dry cycles at home. It came out of the dryer perfectly, duct tape intact! So to this day it still bears the marks of that fast fix.