Omnidyne-M Mammoth

Mammoth is unique in that it's primary weapon is actually good - it is the only frame in game whose natural primary weapon is good on it's own. With extremely high rate of fire and weapon area - Mammoth can make quick work of both large and small mobs - and since it doesn't rely on abilities for damage, it can use Heavy Armor without worry of blocking HKM charge. Cycling between Thunderdome and Heavy Armor alone is more than enough to keep a Mammoth alive and healthy - and with it's charge it can easily move around as needed.