BT-16

The BT-16 Perimeter Defense Droid is a bulbous, spider-like droid manufactured by the Arakyd Corporation. It comes equipped with highly sensitive sensor packages and a Taim & Bak repeating blaster cannon.

Judging from dialog between two Stormtroopers in ANH, the BT-16 is issued with Imperial forces. The droid was seen in ROTJ, being used as a carrier for disembodied brains of B'omarr Monks.