Bruce Banner has more personalities in his head than George R.R. Martin. Comic books are notorious for playing fast and loose with the origins of their creations.
Gray Hulk - "The Incredible Hulk"
More intelligent than his green counterpart, the Gray Hulk went by the pseudonym of "Joe Fixit" and took up residence in Las Vegas working for a crooked casino owner. Banner, repressed in Hulk's mind, eventually reasserted himself until they began to change places with each sunrise and sunset, with Hulk asserting himself at night.
The Incredible Thing - "Age of Apocalypse"
In an alternate reality where Bruce Banner never became Hulk and mutants rule the world, the human Banner was a member of the Human High Council, the ruling body of the surviving human population.
However, he longed to become a mutant in order to escape being a second-class citizen. Caving in to the moral low ground, Banner sold himself to one of the Horsemen of Apocalypse in order to experiment on mutants and eventually himself. The results were the Thing, a Gray Hulk variant Banner could revert between at will.
Aboriginal Hulk - "House of M"
To control his dark side, Bruce Banner goes into seclusion. Setting up shop among the Aborigines of Australia, they help him achieve peace with himself by detaching from society — until the new totalitarian mutant government threatens the safety of his new friends. Then all bets are off as Hulk teams up with terrorist group A.I.M. to conquer all of Australia.
This story is the lead-up to the much lauded Civil War series.
Infernal Hulk - "The Incredible Hulk"
In a reality where Bruce Banner and Hulk were separated into two bodies by magic, Hulk ended up being cast into hell. Corrupted by the demonic beings he encountered eventually converted Hulk into a demon. Devoid of any sense of good, Infernal Hulk escaped from hell and attempted to kill his creator, Bruce Banner.