The gAtari is a "musical instrument" that basically consists of an Atari 2600 playing pre-programmed tunes, which has been hacked together with a few guitar effects processors. It's kind of like an Atari keytar. The resulting music is scatterbrained weirdness that's impossible to describe.
Old gaming consoles like the Atari 2600 had a pretty limited range of sound effects, but hackers like cTrix have long been taking advantage of the limited tonal possibilities to make crazy sounding "chip music," either by splicing old game cartridges or programming new chips altogether. But cTrix turns it up a notch with the gAtari, which allows him to tweak the music coming out of his programmed chips on stage in real time. Sure, it's not a guitar in any traditional sense, but this video from the Blip Festival in Tokyo pretty much explains why nerds everywhere are freaking out. [Dvice via Topless Robot]