I've recently added an "odd" item to my kit that I'm finding extremely useful - Electrical Lacing cord - aka "12 cord".  OK - it's string, and we all know we should have that, but this stuff is NICE.  It's a nice, anout 1/16th round polyester string (nylon and cotton also available, as are other diameters and FLAT) - but besides that, it's waxed.  It keeps it on the roll, makes it hold knots well.  Downside?  Not cheap unless you can find it surplus - usually available it "natural" (aka white) and UV resistant black.  BTW this is the stuff that was used pre "wire ties" and is still used today in a lot of places