Bonzomatic
A fullscreen shader editor that overlays the code on its own output, built for live coding on stage.
Gargaj (Conspiracy) wrote Bonzomatic as the workhorse for Shader Showdown. It renders a single fragment shader fullscreen and draws the source as semi-transparent text on top. Each successful compile updates the image; a failed one leaves the previous version running, so the audience isn't treated to a black screen over a typo.
The shader receives time, resolution and an FFT of the audio input, which makes it trivial to pulse along with the DJ. The code is open source and has become the standard for live visual coding at demoparties well beyond Revision.