Yes, I'm a bit biased. I'm a fan of CruzTOOLS' solid line of problem-solving musical instrument tools. I own and use one of their Guitar Player Tech Kits [Tape Op #69] (awesome for general guitar tech tasks), as well as a Jack and Pot Wrench [#83] (handy for tightening/loosening the awkward nuts on tone/volume pots). Their Drum Multi-Tool is a godsend to have around the studio; it allows adjustment of pretty much any type of drum hardware, vintage or modern. And I reviewed the ingenious Sound Hole Truss Rod Drivers [#111], which enable the adjustment of inconveniently located sound-hole truss-rods in some acoustic guitars.
I recently got my hands on the newest version of the CruzTOOLS Guitar/Bass Multi-Tool and love it to the point where I want to take it with me everywhere — just in case I encounter a guitar that might need tweaking. (Okay, I'm biased and a bit weird.) But, you know, at the gig or in the studio, temperature and humidity changes can cause guitar problems to crop up. String height, intonation, pickup height, and truss-rod rotation are all things that can be addressed easily, presuming you have the right tools.
Enter the highly portable Guitar/Bass Multi-Tool. Fully folded up, it fits in the palm of your hand and includes every non-cutting tool I can think of for adjusting guitars. This includes four SAE and five metric hex wrenches, to cover most truss rod, bridge, vibrato system, and pickup height adjustments. I should mention that the four truss-rod-sized hex wrenches (1/8'', 3/16'', 4 mm, 5 mm) have ball-ends for easy insertion, without stripping the socket, even when used at a slight angle. There are also one flat and two Phillips screwdrivers. And, new to this second generation of the Multi-Tool, there is now a precision ruler/straight-edge for fret and string-height measurement, as well as a 5/16'' socket driver, for accommodating Gibson-type truss-rods. The tools fold into both sides of a blue plastic, one-piece frame; it's that kind of lightweight-yet-very-tough plastic that vandal-resistant municipal parkbenches are made of.
The build quality is very nice; the tools are chrome-finished pro-grade S2 steel. And the whole thing is not particularly expensive, either. Small and versatile, the CruzTOOLS Guitar/Bass Multi-Tool is perfect for toting to a venue in a gig bag, or keeping handy in the studio, where last-minute guitar adjustments always seem to be needed. $15.95 direct; www.cruztools.com)