When Captain America gained the gamma powers of the Hulk, he became a towering monster capable of going toe to toe with Bruce Banner's alternate form. However, while Cap's transformation was as monstrous as fans might imagine, it actually broke all the rules surrounding Hulk's powers and the way in which they manifest.
At the time, the man wielding the shield was Bucky Barnes - the former Winter Soldier - who had taken over Steve Rogers' superhero identity following his apparent death. While he didn't have the benefit of the Super-Soldier serum, Bucky gained near-identical powers from the Infinity Formula, which added to his existing cyborg enhancements and years of training, first as Steve Rogers' wartime sidekick, then as an assassin for Russia's secret Red Room training program.
It was in his role as the new Captain America that Bucky - in Jeph Loeb and Ed McGuinness' Hulk #21 - was part of a mission to stop the Red Hulk and the villainous Intelligencia, instead being bathed in radiation that, like Bruce Banner before him, turned him into a gamma mutate. Like most of the other heroes affected (including Captain Marvel, Cyclops, and the Human Torch), Bucky grew to a Hulk-like size, gaining super-strength, incredible durability, and a Hulk-level healing factor. Bizarrely, his prosthetic arm was somehow similarly affected, swelling in size and sprouting spikes. While Captain America's shield was no longer needed as protection, Bucky-Hulk was able to wield it as a weapon, even almost bisecting the similarly bulked-up Wolverine.
What's strange about this transformation - and the others that occurred alongside it - is that it's so out of step with the lore surrounding gamma mutation. Since Hulk's origin, it's been confirmed over and over that the form a gamma mutate takes is dictated by their inner life and hidden desires. While Bruce Banner's childhood abuse meant that gamma powers unleashed his rage, his huge size isn't necessarily the only outcome of exposure. Dim-witted Samuel Sterns gained super-intelligence after gamma exposure unlocked his desire to be smarter, journalist Jacqueline McGee gained the power to see other dimensions due to her quest for insight, and while Doctor Leonard Samson did get stronger, he kept the appearance of a stereotypical superhero, since that - rather than unlimited power - was his actual desire. In short, Captain America's 'Hulk powers' shouldn't actually have been anything like Bruce Banner's.
While the transformations of the gathered heroes can be explained by the Intelligencia experimenting with the collected energy and perhaps altering its makeup, it would have been fascinating to see each hero's true desires given literal form through the twisted lens of gamma. While Thor finally became stronger than Hulk due to his transformation, and heroes like Storm got a major boost to their innate powers, Bucky Barnes didn't desire power or superiority, only taking the Captain America mantle to honor Steve Rogers' wishes. As Captain America, Bucky's true quest was to in some way make up for the horrific acts he perpetrated as the Winter Soldier, and it would have been fascinating to see how this desire for redemption manifested via gamma radiation, which has been shown to have near-infinite variety in how it can transform the human body.
The ability to heal or resurrect others would have been perfect for Bucky's transformation, channeling his guilt into powers which allowed him to take back his mistakes - while, of course, ultimately leading to horror, as all gamma powers eventually must. Hopefully, Marvel will one day again hand out Hulk's gamma powers to its assorted heroes with more focus on bringing out their hidden desires, as while Bucky Barnes' days as Captain America may be over, there's still a lot of potential in seeing what the Winter Soldier becomes when his most fervent desires are given free reign.