Catalyst produces hybrid waveforms by taking two oscillators, applying half wave rectification then sticking the results together to form some unusual waveshapes. The focus of the synth is producing some interesting, dynamic waveforms. The concepts may not be that familiar, however the synth has been designed so that each control does something meaningful and useful. There is an in depth manual on the developer's site explaining what's going on 'under the hood' and 64 presets to get you started.
The synth has been featured in Computer Music Magazine: "Different is good and Catalyst is nothing if not different.".
Update, June 2013: The calibration of the control linking the envelope to the filter cutoff has been modified to yield a deeper envelope to cutoff modulation.
The short sound demo is created entirely with Catalyst. No external effects used, just a little mix compression.