Big Man Needs Big Gun

Primary Weapon: QBB LSW (Foregrip, Full Metal Jacket)

Secondary Weapon: SMAW Rocket Launcher

Lethal: None

Tactical: Trophy System

Perks: Flak Jacket, Toughness, Tactical Mask

Wildcards: Primary Gunfighter (Adjustable Stock)

While the little baby men are running around the battlefield with their assault rifles or hiding behind cover with their snipers, you're the big bastard keeping everyone wetting their pants with your giant gun. The QBB LSW is a powerful light machinegun that fires more rounds per minute than any other. With Full Metal Jacket rounds it'll chew through literally anything and anyone. The Foregrip will keep you aiming straight  while the Adjustable Stock gives you some much needed mobility while you're toting this beast.
The rest of this loadout is designed around keeping your bulky ass alive while you're shooting the place up. Flack Jacket and Tactical Mask will keep you stable when everyone gets the bright idea to throw grenades of all sorts at you and Toughness will keep you stable when some damn fool steps out to fire back. The Trophy System may seem like an odd choice, but when the enemy's run out of options they'll undoubtedly drop a few bombs on you and you'll be ready for them when they do.
If someone else decides to nut up and carry a big gun or worse, send out a mechanical monster, pull out your SMAW and blow them to smithereens.