Sonic Finger sell some interesting audio plug-ins, including the
Dead Quietenator, which provides 56 types of digitally-modelled silence, including previously unattainable vintage sileces, and
Virtual Studio Visitor, which, when applied to a track, simulates the effect of a specific visitor watching the performer (presets include "Guy From Label", "Resentful Girlfriend/Wife", as well as generics like "Clown" and "Ninja"):
Man, I so wish I'd known about these when I did the Digital Music book. So very much my kind of thing :)