In Iron Man 3 there is a brief glimpse of a large Iron Man suit that is used to keep the oil rig from sinking.
What is this suit called and what is it used for?
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"Jarvis, get Igor to steady this thing!" ―Tony ordering Jarvis to make Igor hold the oil rig in place, to keep it from collapsing.
Per the Iron Man wiki:
The suit earned it's name the Igor, beacuse it has a similar resemblance to a hunchback, having a slouched and bulky appearance, just like that of an "Igor". It specializes in lifting heavy objects such as debris, and is capable of tremendous strength and power.
Designed for heavy duty tasks that his standard armors cannot handle, TONY STARK creates the HEAVY DUTY BRUTE ARMOR with sheer strength in mind. Equipped with state of the art hydraulic systems powered by a modified ARC REACTOR.
A.K.A the Hulkbuster Armor. Not explicitly termed as the Hulkbuster though, since that's not the intended purpose. It's prototype is the Mk. XXII / v.01, and is smaller and more humanoid.
This armor enables IRON MAN to take on the strongest enemies.
The Brute can be seen in the final scene of the new Iron Man 3 trailer and is clearly inspired by Stark's meeting with Bruce Banner in The Avengers.
The Hulkbuster was a modular add-on, part of Stark's Modular Armor and first appeared in Iron Man #304 (May, 1994). The suit vastly increased the physical capacity of the Iron Man armor, was layered with additional composite armor and additionally hardened against gamma radiation.