Krios Battle Tank
The Krios Battle Tank is the main battle tank of the Adeptus Mechanicus, and unlike most Imperial Tank designs it is horrendously exposed, what with the cogs and gears being placed everywhere for the eye to see. You would think the Tech Priests would have the dignity to armor up their main battle tanks so that it could survive more than a few minutes in a war. Seriously who the hell designed this!
Ranting aside, the Krios is an ancient and arcane tank that is durable and protected by interlocking energy fields (Which I believe off-sets its horribly exposed mechanics, although that is still not an excuse). Its most common armament is the Lightning Cannon which can fuck over most enemy vehicles and tanks, making it akin to a Space Marine Predator, except more incompetently designed.
Variants
Yes, believe it or not, the Krios has another brother called the Krios Venator which changed the role of the Krios from a MBT to a dedicated tank destroyer, swapping its Lightning Cannon with a Pulsar-Fusil (Think a multi-chambered particle beam cannon designed to fire volleys of destructive energy bolts which detonate explosively upon hitting their target), like most Super OP weaponry, the Pulsar-Fusil is guarded by the Mechanicus, only using when they are dragged into a conflict.