There are other threads on here on tools that people think you should have. I think that some of them get way to detailed or try to cover everything to the point where there are tools you dont need.
Here is an quick brake down on what I like to carry, (Im a lighting tech)
-**8" C-Wrench
-*Leather Gloves
-**Flash Light (S)
-*Knife, one that will clip onto the belt, and a normal pocket knife
-Multi-Meter
-Pliers , needle nose and or
channel lock
-Di angle cutters
-thumb cutters
-bandana
-small note book
-pen/pencil
-sharpie black and silver
Things like multi-meter and thumb cutters and others depend on what you're doing and what type of venue you're going into. Also its all personal preference.
The * items are the one I think you should never show up to a gig without, the ** just put emphasis on that tool.
And I think the term gig bag is a fine term