DuctTape is useful at four in the morning when the dog is barking. It is the answer to the world's problems. If DuctTape can't fix it, it needs to be replaced. Curiously, though, it's remarkably ineffective with ducts. Also known as 100MileAnHourTape.
Lee Valley tools sells the original duct tape at http://www.leevalley.com/US/wood/page.aspx?p=56121&cat=1,110,43466&ap=1. This is the stuff you can use instead of handcuffs or patch a canoe with. It's *way* different than the stuff you get at the hardware store.
Originally, duct tape was called duck tape because of its water-resistant qualities.
In case of emergency...
From http://freefall.purrsia.com/
Duck Tape was invented for its water-resistant qualities, for the purpose of sealing ammunition boxes for the army. The fact that it's durable yet tears easily by hand is another feature built into the design. As mentioned above, it's not very good for sealing ducts, as the adhesive will tend to dry out and the tape will fall off, and if used on heating ducts, it just becomes gummy (and again, falls off). I suspect the "Duct Tape" misnomer came about because of its superficial resemblance to the foil tape actually used on ducts (well, it's grey and about the same width) and that no one really believed "Duck Tape" could be a serious product name. It's still sold under that brand name however.
International names for duct tape include:
Witness yours truly characterizing JavaLanguage as ducktape on C++ and consequently getting blasted for using duck tape instead of duct tape on Slashdot:
until a rescuer comes and the matter is settled:
http://www.octanecreative.com/ducttape/duckvsduct.html
Famously, duct tape is like the Force: it has a light side and a dark side, and it holds the universe together.
And it's the Handyman's Secret Weapon...
It's part of the AllPurposeToolKit.
It's effective at removing warts!
From an unattributed Internet article: "At the end of every six-day period, the patients soaked the wart in water and rubbed it with a pumice stone or emery board," leaving the efficacy of duct tape (by itself) unclear.
Speaking as someone with limited wart-removal experience (in the 1970s, dissolved with Compound W), I leave it to others to independently verify the efficacy of DuctTape. It is, however, useful for holding bits of things together. -- SeanOleary
http://www.aafp.org/afp/2003/0201/p614.html cites Focht DR III, et al. The efficacy of duct tape vs cryotherapy in the treatment of verruca vulgaris (the common wart). Arch Pediatr Adolesc Med. October 2002;156:971–4.