Ok, here's some wiring tricks for when you're being all ninja and find some bundles:

Opening Cables:
If you want to identify what a cable is, you may need to open it. To do so without leaving much of a trace, take an exacto blade and cut along the wire in the center of the jacket, about 1" long and just deep enough to penetrate the outer jacket. Spread the jacketing and if there is any slack in the cable, you can spread out the individual wires. Slice a little out of the side of an individual wire to see if it is stranded copper or solid.

Wiring Identification:
Two and four conductor wires with RED/BLACK or RED/BLACK/GREEN/YELLOW are usually alarm system wiring. Other colors may be used, but generally wiring is stranded core copper wire. RED/BLACK are usually used for device power, and the other two for signal (wire loop for alarm zone).

Telephone wiring is generally solid core wire in either RED/BLACK/GREEN/YELLOW or other colors depending on manufacturer.

Network cabling is usually WHT/BLUE, WHT/ORANGE, BLUE/WHT, ORANGE/WHT.


Messing Up a Cable:
If you have a cable that is bothering you, and you want to have somebody go through either a ton of trouble to trace the problem, or just have to completely replace it, try this one:

Take a thin sewing pin and ram it through the cable. Then with a pair of diagonal cutting pliers, cut off the pin where it is outside of the cable. This will short 2 or more internal wires together and will be just about impossible to locate. This is great fun to pull on the office IT department guys. Works with USB cables, speaker wires, telephone and LAN cables, and many others. Obviously not a good idea for power cables.

You should NEVER open unknown wires using an exacto blade. if you MUST open a wire, use either a ceramic knife, (cutting along the wire, not into it) or hold a lighter underneath the cable. Otherwise you run a serious risk of damaging any connected equipment, (accidentally shorting out data and power) and killing yourself. (AC power)

Also there's no UE related need to EVER 'mess up a wire' like that. Putting a pin in an ethernet cable could easily damage expensive PoE hardware; in a phone line, it could prevent somebody from getting help in an emergency.