Probably the most common connector in the audio world is the XLR connector.  It is also called mic, Cannon or 3 pin.  Most professional microphones and mixers use the XLR connector.  Advantages of XLR include locking connectors, pins only contact their corresponding pins and strong metal housing.  Disadvantages of XLR are large connector size and occasional failure of the locking mechanism.  While it is my understanding that it was originally designed by Cannon as a stereo audio connector, 3 pin XLR is almost exclusively used with a mono, balanced audio signal.  In modern usage pin 1 is connected to ground, pin 2 to positive signal and pin 3 to negative signal.  Shielded, untwisted cable is typically used for XLR cables, though you may come across star-quad cable which has two twisted pair cables for pin 2 and 3.

XLR is not only used in Audio, nor does it only come in 3 pin varieties.  A quick search will turn up XLR connectors with 3, 4, 5, 6, 7, 8 and even 12 pins.  Three pin cable is also commonly used for DMX signal in lower end lighting (though some high end companies have given in and started adding them as well).  Note that for lighting unshielded twisted pair should be used.  I’ve seen 4 pin in use for single channel com headsets, power cables for studio cameras, and powered signal cable for LED lights.  5 pin is used for stereo com headsets, and as the standard for DMX lighting. 6-12 pin XLR are much more rare to see in the AV world, though they do occasionally pop up.

Hopefully the next time you pick up that mic cable you will have a new appreciation for the XLR connector.