Of course you know the rhythm box/drum machine has had a profound impact on modern music-making, but how much do you know about its history? Was the Rhythmicon the very first rhythm machine? Korg's DoncaMatic (great name, eh?) was one of the first commercial models. Up until 1979 they were all pre-programmed, but Roland ushered in the modern era with the user-programmable CR-78, and followed it up soon after with the legendary TR808. Go here for a fairly comprehensive overview of vintage drum machines (organized alphabetically, with photos and descriptions/background info). And here you can interact with a wide assortment of virtual [Flash] rhythm boxes of the 70's and 80's. (Knee-jerk Flash haters, go ahead and hate it, but this is one of the best uses of Flash I can imagine.)
The piatarbajo, the chromelodeon, the trimba, cloud chamber bowls, the simeon, the pyrophone, the virtual rhythmicon, cigar box guitars, the skatar, and all the other assorted instruments by musical visionaries who find guitar, bass, drums, and the symphony orchestra too confining.