Big update in my hand-made guitar collection:
I recently got a Dremel tool and a routing head. So, as an experiment, I added some S-holes to my full-length two-string cigar-box guitar. The openings allow vibrations to transfer better to the surrounding air, so it's actually louder and bit richer-voiced.
Excited by the good results, I cut somewhat larger S-holes in my full-size three-string cigar-box guitar. That sounds even better!
As an added bonus, the S-holes (like F-holes on a violin, but without the cross-cut. Technically, any shape of hole would have done, but these look prettier) make them symbolically more like guitars, as opposed to boxes with sticks and strings attached.
Sort of in the other direction, less trying to make a handmade object more and more like a "real" guitar, I tried to see how far from a real, full-sized guitar I could get and still call it a guitar.
Thus, the Mix-o-Caster, a single stringed one octave guitar made from a small wooden mixing spoon, an eyebolt, two nuts, two washers, two small segments of basswood, and an acoustic guitar string. It actually sounds quite lovely, and if you contact it with something like a door or a PC-case, that object will act as the soundboard. Quite a versatile little guitar, and it fits right in your pocket.
Here's my full-sized with S-holes, the ukele-sized mini, and the Mix-o-Caster side-by-side for comparison:
Possible future plans include a cigar-box hammer dulcimer, a cigar-box thumb piano (lamellophone), an Altoids-tin mini-guitar, a musical object made entirely from Ikea crap (I saw the bins of replacement parts that they let you take for free, and my heart started racing).