Your War Machine.

[Blemontea]

Left Arm: Ballistic Stiletto Sword, acts as both cqc and a ranged weapon example: The arm blade in Human Revolution.

Right Arm: Incendary Automatic Shotgun

Shoulder: Machine Grenade Gun from New Vegas

And two hip side uzi machine guns for an extra medium range rapid fire, and standard fire pistol.
If that don't count then at least i have the other weapons.

 

[Hero in a half shell]

The usefulness of the suit seems to primarily be allowing you to lift heavier stuff, and not much else. They don't show any agility demonstrations so I'm assuming it's pretty cumbersome, which is not what you want if you're vunerable in a firefight or trying to working with a team. I would cover the thing in titanium plates, pretty much the best protection there is, and make it bulletproof:

Spoiler: It would look something like this...

As there are tanks, Planes, and artillery for heavy weapons in the great outdoors that the mech couldn't compete with, I would class the mech as an indoors, close quarters, heavy duty, anti-personnel "vehicle". The durability of a tank with the size and manoeverability of a man. Give it akimbo AA12 automatic shotguns, a grenade launcher set on the shoulder Predator style, and maybe a retractable blade on the main arm for messy close combat situations. Also build in other useful features: a torch, flares, wirecutters/other basic tools.

I would expect it to be used in house to house fighting, where blowing up every building isn't an option. I'd imagine three of these guys could take on dozens of regular soldiers, You'd also be much safer patrolling the streets in one.

 

[Nouw]

Shoulder:Micro 'Fire and Forget' Nuke Launcher.
Left Arm:Lasers.
Right Arm:Chaingun.
CQC:Flame-thrower.

What classic Mech am I trying to create here?

 

[DischordantMind]

Wow, okay, a thread on an "Over Kill" weapon of sorts.

What about something which leaves the country intact once it has been activated? Hard to concieve of, perhaps.

Surely one that doesn't expend any ammunition at all? For me it would have to be one which removes the will to fight in the enemy completely. Psychological warfare of some kind. The room for abuse would be massive though, like any weapon.

But...if all else fails, send in the Mechs/Armoured Cores/Gundams etc.

Its certainly more fun that way.