OD-Octave
I was looking to emulate my Boss OC-3 Pedal which features both Octave and fuzz, I tried the MOD Guitarix OC-2 emulation and the MOD MDA-Subsynth but both were pretty messy and lost tracking pretty quickly especially when playing fast. I was able to utilize the 2Voices plugin with the Tubescreamer and get a righteous Octave fuzz that tracks nicely. 2Voices is set to have 'Step1' dropped an octave and Step2 retains the original actual pitch. Unfortunately there was not enough spare CPU to record a sample.