“It's so much easier to see the world in black and white… Gray? I don't know what to do with gray…”
Very long, complicated, and containing more spoilers than TVTropes, a detailed account can be found right here for reference.
Long story short, he was a disenchanted investigator on a space station rivaling the size of one of Earth's major metropolises. He joined up with Commander Shepard to save the galaxy from a giant space squid of death. Then became Batman, got himself declared dead, and saved the galaxy again.
Garrus has been described as a hothead with an itchy trigger finger. He chafes under restriction, preferring to do things his own way, rather than "by the book". He has a strong sense of right and wrong, however, and most of his "outside the book" efforts go towards bringing the criminals to justice any way he can. He highly respects individuals whose efforts are geared in this same vein. When he is unable to do this, it eats at him, and is not lightly shaken off—failure does not agree with Garrus—if anything, it only gets worse the longer he is unable to do anything about the situation.
Overall, he is a highly dedicated, loyal man, who would take action over sitting around talking in a crisis. If you have his respect, and therefore, his loyalty, he will follow you to the ends of the earth. He cares for his crew, whether they are on equal footing, or have a superior-subordinate relationship, very deeply. He idolized Shepard, in the beginning, and while that didn't change over the years, some of it seemed to rub off. He became more comfortable in the Commander's company, but, it seems he always will hold Shepard in highest regard.
His mission goals are of the utmost importance in his mind, above all else, even the needs of others—save for those in his squad. Duty is important to him, and he is easily frustrated when he can't do what he has deemed to be his. His turian upbringing dictates that he places the good of the many over his personal goals. He sees things in, as he says, “black and white”. Either someone is innocent, or they're a criminal. “Gray is… difficult,” he tells Shepard at one point, indicating that when the facts point in different directions, he starts to lose sight of what it is that needs to be done.
Garrus' personal life is disastrous. He makes an abrupt switch from the jaded, world-weary sort of rogue-cop he's become, and turns into the galaxy's most painfully awkward teenager going for his first date. He can be racist, taking a broad view of a certain race, but is, as evidenced by his conversations with Wrex and Tali in the first game, willing to change his views on an individual basis.
Garrus is a turian, a tall, bipedal, bird-like species, who is a capable hand with most firearms, most specifically sniper and assault rifles. Outside of that, he is decent enough with electronics, being able to do some hacking. He's better at making repairs on said electronics, and even automotives when the need arises. He's had police training, due to his former occupation, and was, by most accounts, a very good investigator. At one point, he states he was considered one of the best in hand-to-hand combat during his military service, and is renowned for his sniping ability.
Garrus' turian biology gives him a small amount of resistance to radiation, as well as sharp, elongated talons on each hand and foot. However, due to his genetic make-up, he could very well experience a deadly allergic reaction, should he ingest any material that is not based on the same genetic material as the turians themselves—that is, anything not produced on their homeworld.
In general, turians "exhibit the characteristics of predators rather than those of prey species. Their forward-facing alert eyes give the impression that they possess outstanding eyesight and their teeth and jaws mimic the structures possessed by apex predators such as crocodiles or ancient, carnivorous dinosaurs. Needless to say, their talons on both their feet and hands seem capable of ripping flesh. Their slender bodies also seem to suggest that they are also capable of moving at high speeds" (As quoted from the Mass Effect wikipedia entry on turians.)
Because of his life on the Citadel, a galactic hub, it's reasonable to assume Garrus is multi-lingual. He at least speaks his native language, as well as the major human dialect (English, for the purposes of this game). It's stated in Mass Effect canon, that the asari language is predominant on the Citadel, so, therefore, it's likely he can speak it conversationally as well.
UNDER CONSTRUCTION der hur
- Aya Brea: Reminds him of Shepard. Fellow officer. Thinks she's overworked. Severe bromance.