Perhaps it would be good to have turrets from all families, so that elemental guns are not the end-all for turret slaying.

Ideas:
Beast,
A large flightless bird, perhaps akin to a vulture that has eaten FAR too much. As to its unique quirk (See polyip's Omnidirectional sight, Exploding Howlitzers, and Rocket puppys.) when it spots a knight, it will attempt to strafe around the knight, flapping awkwardly and sputtering all over until it fires a batch of feathers. It moves slower then a lumbar.

Gremlin,
A small Knocker retrofitted a seat atop a Gun puppy (Or Rocket puppy) and now goads it to attack faster, and turn faster.

Fiend,
A devilite leaps atop its desk, eager to inflict pain on the knights that come near. It fires all of the tier appropriate projectiles at one knight. Yes, they move fast, are random office supplies, and move as fast as a devilite's attack. But it has the range of a devilites toss, which is not as far as any of the other family's. They also track a little slower then the others, for trying not to step on it's paperwork.

...Can be put into overtimer rage/Yesman status. Yes men go right back to work.