Thorin II Oakenshield
Undoubtedly the most famous of the three Thorins that were descendants of Durin the Deathless was Thorin the Second, called Oakenshield. He was the son of Thráin II, and is first mentioned as fighting in the Battle of Azanulbizar, in which the Dwarves, led by Thráin, defeated the goblins under Azog. Legend tells us that Thorin gained his name when, having his shield cloven by a goblin, he cut off a staff from the branch of a tree and used it to fend off blows.
Although the Dwarves were victorious at Azanulbizar, Thráin was deserted by all but Thorin and a small following of Dwarves. Accompanied by Thorin, Thráin returned to Dunland, and later took the company northeast through Eriador and into Forlindon, possessing no more than a ring -- yes, one of the seven made for Dwarves by the Elven-smiths of Eregion. A short while later, Thráin wandered off, doubtless not quite sane, and somehow found his way into the dungeons of the Necromancer of Dol Guldur (later identified by the Wise as Sauron). There he died, presumably of slow torture, survived by his son, Thorin Oakenshield, now a young fellow of ninety-five. His small band expanded as other Dwarves heard of his kingdom in the north-east, and things were not badly off.
Gradually, however, Thorin became seized of the jealousy so typical of Dwarvenkind. What was he doing here, living homeless in the West, allowing a dragon to possess the mountain that should be his by rights, Erebor? And due to some strange turn of chance (or the old prophecies about the King Under the Mountain coming true, Thorin got a chance to retake what was his. Staying at an inn in Bree, Thorin happened to meet Gandalf the Grey, fully certified wizard. Thorin happened to know what Gandalf looked like, and at their meeting, it was found that they had a common objective -- to eliminate Smaug, the Dragon that now ruled Erebor (Gandalf was afraid that the Necromancer would somehow be able to make use of the dragon). With the help of some dwarvish companions, Gandalf, and Bilbo Baggins, a hobbit of the Shire, Thorin reached Erebor where Bard of Esgaroth slew the dragon. Sadly, at the subsequent Battle of Dale, Thorin was mortally wounded, and died peacefully, knowing that The Lonely Mountain would now be ruled by his cousin Dáin and would belong to Dwarves forever. (Well, so he thought. But we all know that after the end of the Kingdom of Gondor began the Age of Men in which the other races passed into myth)