I specifically enjoy animating mechanical and giving character to non-characters. Fortunately these tasks are often low priority for the animators and I've had the opportunity to add my own flavor to these models.

Forsaken Catapult
Well of Souls
Proto Dragon

Rig Feature Examples:

Several rigs had additional features built into them. Rumble, squash-and-stretch, and dynamic tentacles shown below.
Animations by Corey Pelton, Carman Cheung, Steve Aguilar, Mauricio Hoffman, Jason Zirpolo, and Bryan Gillingham.

FelReaver Mech