Since We’re Talking About One-Man-Bands, This Dude Rules
No conversation about the idea of a one-man-band is complete without talking about the Australian musical genius Juzzie Smith. Not only does he rock a full ensemble by himself in that bluesy style, he's made most of his own instruments down to the three-string Delta guitar. If you look closely, the body is cigar box.
If you want to try this stuff yourself, you can buy one of these epic Southern Americana three-string guitars from several places online... But it's much cooler to order a kit and build it yourself.