Obi-wan Kenobi, AKA Old Ben, was responsible for helping to turn Anakin Skywalker into Darth Vader but to make up for it he started training Anakin's whiney son in the ways of the force, sorta.
Obi-wan was trained by Qui-Gon Jinn to be a Jedi Knight (Though when older Kenobi claimed it was Yoda because he thought Yoda was cooler and had once been on Galaxy Idol - all the way to the final four!) Somewhere in his late teens he became addicted to Spice and hung around some questionable fellows while sleeping with his underage girlfriend. Eventually though, he found his way back to the Jedi where he and Jinn seemed to just sweep the whole affair under the rug. They were then sent to Naboo by the Supreme Chancellor like little errand boys.
Training a Whiny Kid (Take 1)
After fleeing Naboo like little girls, Qui-Gon attempts to dump Obi-wan for someone better. A ten year old kid name Anakin, who
some how wins an important race, seduces a 15 year old Queen, and does a worse job showing emotion than Mark Hamill in ANH. Obi-wan gets all jealous, but after Qui-Gon goes and gets himself killed, Obi-wan agrees to train the kid.
Obi-wan does his best to train the kid, even after ten years he's still whining about missing his mother and obsessing about a girl he knew all of two weeks. Then after all his hard work, the kid almost gets them killed by a Sith lord because he wouldn't listen. Eventually Anakin does just what Obi-wan told Qui-gon he would do by turning all evil. But because Obi-wan had become a pussy hanging out with Anakin he didn't bother to finish the job and kill him when Anakin turned evil.
Training a Whiny Kid (Take 2)
After hiding out for twenty years Obi-wan finally decides to man up and try and fix the problems he created for the Galaxy. He took Luke Skywalker under his wing to train but quickly realized that Luke was even more of pussy than his father. After giving Luke a bare minuim of training, he goes and lets Vader kill him just so he wont have to deal with the whiny brat. After that he got to chill as a ghost and drop in on Luke and leave when he wanted and also check out Leia in the shower cause 'hey, she's not my kid.'
He then passes the task of training Luke off to Yoda, who totally tried to get out of it, but Obi-wan lied and threatened blackmail concerning some photos of Yaddle and Yoda. After that Obi-wan just hung around the women's showers and teased the Emperor in his bedchamber.
LightsabersObi-Wan officially had two lightsabers. He at first had his knobby one as a Padawan, then borrowed Qui-Gon's for a bit. He was able to retrieve his knobby one from where Darth Maul had kicked it, and used it until the Clone Wars. Presumably Count Dooku threw it out, and then Obi-Wan built a new one.
There was one other saber he borrowed at the Battle Of Geonosis as well, but he gave it to Anakin and it got brokey. He also did use Anakin's for a moment during their duel on Mustafar, but no one really noticed.