Inspired fan art from Halo Reach.
Spartan Heavy Arms variant is a colloquial term for Spartan armor that has gone under heavy customization to improve plate density in multiple areas. This particular suit has been grafted with multiple extra parts and plates to improve shoulder defense, as well as torso and shin protection. A lighter, asymmetric neck guard has also been riveted in.
An experimental Mark 2 Tank Buster weapons system has been mounted onto the suits back, providing anti-armor capabilities for mobile teams. Using a small guidance package, these 40mm AP/DHE rockets can disable most heavy ordinance.
Heavy Arms variant armors are used by Fire Team leaders who need need ample protection to combat both the duress of an extended heavy fire situation, and appropriate HUD packages to direct their team with pinpoint accuracy. Though a bit heavier then a standard Mjolnir suit, most Spartan Heavy Arms users can run just as fast as their counterparts.
Update: YAy! Thank God I got front page on halo.bungie.org! Time for cake! [link]