Character Analysis
Gawain is the oldest of the G-boys. Red-haired, big, brawny, and hot-tempered, you can't get much more stereotypically Scottish than this laddie. In fact, he flaunts his stereotype, and beefs up his Scottish brogue just to make darned tootin' sure that everyone understands where he comes from, and that he's not one of those bloody English pigdogs (even though he's related to them and pretty much becomes one by the end). His motto is "Up Orkney, Right or Wrong" (Q.1.57). Sort of like: America, Love it or Leave It… but in relation to his family.
One random detail which ends up being a plot device: Gawain loves fruit—especially apples and pears.
In Need of Anger Management
Gawain's defining trait is wrath. He's one super angry guy, and flies off the handle at almost anything. In fact, he once gets so angry that he cuts off a woman's head. He also kills one of the Romans during peace negotiations during the Roman campaign. Because of his anger and willingness to engage in manslaughter, Gawain gets blown off during the Grail Quest. Hardly any adventures come to him.
He also knows how to nurse a grudge. Arthur notes that Gawain is "a decent chap, but he will hold it against you inside himself" (K.9.26). This means that he'll never forgive Lancelot for unhorsing him that one time at the tournament. And how! In the end, Gawain contributes to the downfall of the entire brotherhood of knights because he can't accept that Lancelot accidentally killed "our wee brother Gareth" (C.8.304), and so keeps the feud between the two families alive.