I just listened to a Balthazar dialog, and I think the one effect I have not mentioned yet is the pitch shifter. The audio track has a pitch-shifted, octave down component mixed in with the normal voice. I believe that, along with a good mic of course, is what gives you the low grumbly tone. A vocoder could do something similar (a la Mr. Roboto), but I am pretty sure we are hearing a pitch shifter in this case.
