The droid's flat head provides a minimal target profile: it also contains a sensor package that excels at picking up residual heat signatures. Two spotlights are located on either side of the head--these lights are used to blind and disorient targets, preventing them from mounting last-ditch defensice atttacks. Manipulator arms fold up within a small belly cavity. Thick track treads provide mobility and are capable of a top speed of thirty kilometers per hour.

IG Assassin Droid

The IG assassin droid is the most coldily efficient killing machine ever invented. Its programmers, smugly assuming the could control their creation, gave it unprecedented creativity and intelligence. They paid for their arrogance with their lives.

Roughly humanoid in shape, eash IG's blaster-resistant armored frame stood two meters tall. A cylindrical head, studded with glowing red sensors, allowed the unitto see in all directions at once. The droid lacked olfactory detectors(a nose), but compensated with advanced auditory, radionic, movement, and temperature sensors. Its multiple optic lenses could access a wide variety of spectral filters under hazy or low-light conditions.

The IG's weapons complement was astounding, especially when one realized that the entire arsenal was integrated directly, and unobtrusively, into the standard body structure. Each forearm contained a repeating blaster cannon. A concussion grenade launcher was built into the left hip. And behind various panels and ports lurked a flamethrower, a sonic stunner, a paralysis cord, an array of throwing flechettes, and a rack of poison gas canisters.

The fingers of the right hand doubled as miniature cutting lasers. The mirrored palm of the left hand was capable of intercepting blaster bolts and deflecting them back alon their original path. The IG could also dramatically raise the temperature of its exterior plating, allowing it to burn through nets or melt a stream of immobilizing Stokhli spray.
Description taken from "The Essential Guide to Droids"

Scarab Droid

Their primary target is on the neck.