The BNK3R is a large Hyperion craft, created to guard Angel. It is a fully-automated assault ship equipped with six turrets and a laser. Overall, BNK-3R is a tough opponent, but a cluster of optics at the front and a large swivel eye underneath offer some readily accessible critical hit spots. The turrets are similarly vulnerable targets.
Handsome Jack refers to the BNK-3R as if it were a stationary placement right up until its encounter, where he reveals that it's actually an aircraft.
Drops an above average amount of loot, including Eridium bars and several loot types, even on single player. Make sure you have plenty of inventory space before this fight.
Unique heads for every class
When BNK-3R destroyed it will disperse loot across the entirety of The Bunker. Care should be taken when searching for loot as many of the items will fall into the gaps in the floor. In addition to the loot strewn across The Bunker, BNK-3R will continue to "drip" loot from its main cannon 3 - 4 times.
BNK-3R may sometimes get stuck upon the top level of the complex, preventing it from being destroyed. Jumping onto it from a higher point may sometimes free the BNK-3R, otherwise a restart is required.
If B0re is enabled for Zer0, it is possible to hit multiple hitboxes on the sides of the BNK-3R with even a single bullet, causing massive damage outputs. However, the exploit sometimes causes BNK-3R to glitch and rendered unable to be interacted with.
Triggering the exploit in multiplayer while multiple players are attacking the BNK-3R can result in the BNK-3R dying and crashing where it is without first relocating to the front of the Bunker. Consequently, it can land on one of the circular side walkways, making the loot obtainable, but it can also explode in mid-air, making the loot impossible to get.
Trivia
The number on BNK-3R's intro graphic, 00101010, is binary for 42. The number 42 is "The Answer to the Ultimate Question of Life, the Universe, and Everything" in "The Hitchhiker's Guide to the Galaxy" franchise.
According to Inside the Vault: The Art & Design of Borderlands 2, sound designer Joshua Davidson provides BNK-3R's voice. "When you hear BNK-3R taunting you, it's really just me yelling about tea through heavy audio processing."