Strongly recommend this plugin. The formant pitch shifting is pretty much the only way I can get a good femme vocal recording from my testosterone laden cig-y vocal chords. The rest of the Soundtoys collection is pretty fantastic, but replacable. Alterboy is the only plugin I know of that lets you pitch shift the way it does.
Well if you're pirating them anyway -
I didn't recommend Waves Vocal Bender because their licensing model sucks and they're Israeli; it's the same thing as Alterboy but zero-latency so you can track with it. I actually like it better than Alterboy for that reason