A hero appearing in DC Comics. Guy Gardner first appeared in Green Lantern #59 in 1968.

Guy Gardner is the result of a breeding program begun on Earth thousands of years ago by a group of aliens known as the Vuldarians. A dying race, the Vuldarians introduced their genetic patterns into the human race, in hopes of spawning a Vuldarian-human hybrid that would be able in years to come to oppose their enemies the Tormoks, a ravaging race of aliens who spread death and destruction in their wake. The ultimate result of this breeding program was Guy Gardner.

Gardner grew up in no spectacular manner. He excelled at football and went to college on a scholarship. He stayed in school and went to law school and later went to become a public defender. Unbeknownst to Gardner, when the alien Green Lantern Abin Sur crashed on Earth and sought a replacement, the ring found two appropriate candidates: Gardner and test pilot Hal Jordan. Because Jordan was closer, he was chosen to be the successor to Abin Sur and receive his ring and become the next Green Lantern. Gardner ended up meeting Jordan when Jordan served time for a drunk driving charge in which one of his friends was killed. Gardner represented Jordan.

Years later, Gardner was injured while attempting to rescue a group of children from a bridge collapse. Because of his injuries, when Jordan needed a replacement to stand in for him as Green Lantern, John Stewart was chosen as the replacement. During this time, Gardner began a relationship with a psychic named Kari Limbo. Gardner professed his love for Kari, but soon afterward, a series of events began that would tear the two of them apart.

Gardner was approached by Green Lantern Hal Jordan to fill in for him while he returned to Oa, the home of the Guardians of the Universe, to find out the cause of an issue he was having with his power ring. Jordan gave his power battery and another ring to Gardner, little realizing that the actual issue was with his power battery. With Jordan gone, Gardner tried to recharge his power ring and found himself pulled into the phantom zone, where he was captured and tortured by the villain Sinestro. The torture caused brain damage in Gardner.

Meanwhile, Jordan returned and found Gardner had disappeared and believed that he had been killed. Jordan met Kari Limbo and the two began a relationship. The two fell in love and were to be married, when Gardner was able to contact Limbo via her psychic powers. Of course this happened during the wedding ceremony, and Gardner already unhinged from his battle with Sinestro and time in the Phantom Zone, snapped. Jordan with the help of Superman entered the Phantom Zone to rescue Gardner, but ended up battling both he and Sinestro. Eventually, Jordan was able to subdue Gardner and return him to Earth, but the battle left Gardner in a coma. Jordan and Kari Limbo called off their wedding, because of Gardner's return.

For many years, Gardner was in a coma, but he eventually awoke, though his personality had greatly changed. The caring, compassionate man was gone replaced by a rough, crude man whose brusque manner alienated many people. Gardner became a member of the new Justice League International and served with them for many years. His brain damage caused him to change personalities for a time, becoming somewhat meek and accommidating (think Mr. Rogers). This personality change came after being punched in the face during a fight with the Batman, after Gardner challenged the Caped Crusaders leadership. Gardner later returned to his former brusque nature after he received another blow from the intergalactic bounty hunter Lobo. During this time, Gardner began a relationship with the heroine Ice, though they later broke off their relationship.

Gardner's manner brought him into conflict with Jordan on a number of occasions and eventually the two fought to determine who would be the Green Lantern of Earth. Gardner was lost and stripped of his ring. His desire to continue as a hero caused him to trick the intergalactic bounty hunter Lobo to search out the yellow power ring used by Sinestro. Thus armed, Gardner adventured for a time, but found that the ring would fail on him in battle and that he could not rely on its power.

Still desiring to be a hero, Gardner sought the help of fellow JLA member Blue Beetle who constructed for him a suit of armor. Thus armed, Gardner ceased his affiliation with the Green Lantern Corps and took the name Warrior. Gardner chaffed over not having powers of his own and went with an adventurer named Buck Wargo and his team of monster hunters to the original home of Vuldarians. There Gardner drank the Warrior Waters that were there, which unlocked his Vuldarian heritage. Gardner gained the ability to increase his mass as well as to transform parts of his body into weapons and blades. Thus armed, Gardner fought against the Tormok and defeated them.

Gardner retired from adventuring for a time opening up a chain of hero restaurants. When the world was attacked by the forces of Imperiex, Gardner returned to active duty, but was killed by one of the Imperiex probes.

My thanks to Jet-Poop for his reminder of the circumstances of Guy's personality switch.