Being a suit focused entirely on long-range bombardment and distanced combat (missles all over the body + gatling gun) you figure it would be a very sticky situation if it were forced into close combat.
That's where the Heavyarms' Swiss Army Knife comes into play. While fairly small compared to other suits that sport wicked giant sickles (Sandrock) and beam tridents (Shenlong) the knife is enough to allow the Heavyarms to hold it's own in combat.
Liked it better on the original Heavyarms where it was under the forearm instead of on the side. Still, they did a good job redesigning it to make it bigger and look more lethal.
Came in all gray at first; had to paint the edge a nice silver to make it look decent.