I've been doing some research to find new synths to increase my palette of sounds. Along the way I "re-discovered" Crystal which is a very cool Semi-Modular synthesizer. It reminds me a little of Zebra 2 and Absynth 4 but - it's free! Pretty amazing considering the feature set - "...semi-modular software synthesizer featuring both subtractive syn and frequency modulation (FM) synthesis. It offers abundant modulation control with over 90 parameters which may be modulated, multi-stage envelopes with graphical editors, extensive tempo sync of envelopes/lforates/delay times, built-in effects for chorus/flanging/comb filtering/echoes, and a band splitter for effects processing by frequency band. Not only that, Crystal has wave sequencing, granular synthesis, program morphing, MIDI learn, and imports soundfonts. The musical applications for Crystal are literally boundless."
Installation is manual but straightforward. Simply follow the instructions on the download page. Don't forget to grab the additional waveforms and patches.
As I mentioned this synth is free and the developer, Glen Olander, says creating Crystal is a "labor of love, so I don't accept payments from Crystal users." He does accept donations on behalf a senior center though so if you want to donate go to the bottom of the about page.