Tek'it Audio has some really great VSTs available for free, and the Genobazz series I have used quite often. It's a quick and easy way to add a nice fat bassline to your productions. You have your choice of 8 different waveforms, 8 different filter types, sub boost and full MIDI automation support for sequenced tweaking. There are just two little quirks that keep it from being perfect. First, all the knobs rotate smoothly (as opposed to having graduated increments). This makes it a pain to do fine adjustments because you have to turn the knob very carefully to not overshoot your mark. EDIT: Thanks to Tek'it Audio for pointing out you can make fine adjustments by holding the Ctrl key as you adjust the knob.
Second, even though recent updates have mostly resolved this issue, some of the presets are out of tune by default. And yes, this can be fixed with the pitch knob, but that echoes the first problem again.
Aside from my two minor gripes, it's a great piece of software. Of course, I DID just get the Pro version, so we'll see how that improves on this!