Syntakt lets you route any of your synth tracks or external audio sources through the FX block. This gives you analog distortion and filtering, and a couple of LFOs to go to town with. Additionally, you can also call on Delay and Reverb as powerhouse send effects.
And all of the above effects can be sequenced with the FX track. Have them kick in at just the right moment. Add accents and dramatic changes to the selected tracks or external audio. Or use it as a master track for ducking and gating effects.