Guy Gardner, "Earth's Other
Green Lantern," was a scrappy kid from Baltimore who fought through adversity to become a superhero, "the only job I can take out my aggression and do some good at the same time."
Although he was picked by the Green Lantern power ring to become Green Lantern, dying alien Abin Sur chose Hal Jordan instead because he was physically closer to the alien's wrecked ship.
Eventually, Guy was trained as a Green Lantern. But his first years as a hero were very difficult. First, his body was nearly shattered after being hit by a bus, and he had to walk with a cane for many years. He was given a faulty power ring which sucked him into Hal Jordan's power battery (the power battery is the 'charger' for Green Lantern rings; it's the thing that actually looks like a Green Lantern). Trapped in this dimension, he was forced to watch his girlfriend Kari Limbo fall in love with Hal.
Soon after escaping the battery, Guy suffered mental injuries that put him into a coma. He was released from this coma by a group of rogue Guardians, and ordered to lead a group of supercriminals on a questionable mission. Tortured, tormented, and manipulated, Guy Gardner never lost his urge to be a hero.
After his time in "Comaville," Guy was mainly portrayed as an idiot. His circular red mop of "Moe" hair symbolized a character who was violent and arrogant, yet clownish and impulsive. Although most would consider this a bad combination, it was actually an interesting contrast to the rest of his super-heroing compatriots in Justice League America.
While most of the League were pious, navel-gazing thinkers who would debate philosophy in the middle of a fight, Guy was a no-nonsense action hero, closer to Bruce Willis than Superman. Most of the other superheroes hated him for this behavior, constantly belittling him despite his heroics. He struck up an interesting relationship with the "innocent girl" of the group, Ice, which ended abruptly after she took Superman's side in an argument.
Eventually, Guy withdrew from the Green Lanterns after losing a fight with Hal Jordan over stewardship of Earth. Now powerless, Guy channeled all of his tenacity, persuasiveness, and resourcefulness into regaining super powers.
After failing as a gunslinging hero a la Punisher (but pulling off an hilarious parody nonetheless), Gardner hired interstellar hitman Lobo to help him unearth the most powerful weapon in the universe, the Qwardian antimatter universe ring once worn by Sinestro.
After besting Sinestro's spirit in a dual of wills, Guy took the antimatter power ring as his own, using it once again to fight crime on Earth and in space (much to the chagrin of the superhero community at large). He hired a press agent named Bucky Sharp to "build him up" as a great hero. He currenly lives in a rundown tenement a few blocks from Times Square with Golden Age superhero General Glory, whom he considers a fine American. Guy enjoys cold beer, John Wayne movies, and trips to Scores.