"B" is for "Belcher"

Belcher

Hit Dice:  12
Frame:  Armature
Locomotion:  Treads
Manipulators:  Pincers
Armor:  Duralloy (AC 3)
Sensors:  Class II
Mental Programming:  Programming
Accessories:  Tool Mount
Weaponry:  see below
XP:  2,000

The robots now known as belchers were amongst the first generation of commercial domesti-droids, and mass-marketed as Vacuu-Trak Home Cyclones.  Designed with "retro" sensibilities to appeal to the "hip" consumer, they were man-sized 'bots with bulky frames, treads, grasping pincers, and chest-mounted, telescoping suction-cleaners.  The Vacuu-Tracks would methodically move through a home, lift the heavy furniture, and vacuum underneath.

But after hundreds of unfortunate...incidents...involving toddlers and pets, the Vacuu-Traks were quickly recalled.  Desperate to recoup their losses, the manufacturer converted them for battlefield use by reversing the suction units, enabling the Vacuu-Traks to spew crowd-controlling agents and chemical weapons.  Belchers were born.

Belchers are immensely strong, and attack twice per round with pincers that do 1d10 damage each.  And the robots can spray any number of gaseous substances—nerve toxins, sensory irritants, obscurring smokes, hyper-allergic pollens, acidic sprays, etc.—in both clouds (that surround the robot) and cones (that project away).  [The Mutant Lord should create the specifics of each chemical, including size-radius and specific combat effects.]