Obi-Wan defending the strikes from Darth Starkiller's blade.
Obi-Wan Kenobi was a highly respected Jedi Master during the Clone Wars. He is a powerful warrior who has been honored for his victories against Darth Maul as a Jedi Padawan and General Grevious as a Jedi Master. Obi-Wan has trained powerful Jedi such as Anakin Skywalker and Luke Skywalker. He was trained in the ways of the Force by Jedi Masters Qui-Gon Jin and Yoda. He went by the nickname of Ben when he went into hiding from the Galactic Empire.
PROXY's Training Unit
Starkiller's robot side-kick, PROXY, has a younger version of Obi-Wan in his training programmings to help prepare the apprentice for battle and also his many failed attempts to catch him off guard and kill him.
In the intro cutscene to the TIE Fighter Factory level, PROXY turns into Obi-Wan and attempts to catch the Secret Apprentice off guard by fails at doing so and is easily defeated.
While the soon-to-be Rebel Alliance is meeting on the planet Corellia, Darth Vader and his Stormtroopers attack in the meeting. Darth Vader force pushes Galen, causing him to hold on to a mountain cliff. PROXY attempts to defend his master by attacking the Sith Lord using the Obi-Wan Kenobi training unit but the robot fails and gets stabbed while being badly damaged, but is quickly revived afterwards.
Weapons
Obi-Wan is mostly seen with a Lightsaber with a blue crystal, although he has been seen various times stealing pistols from enemies and attacking them with the weapon in close range.
Death
Obi-Wan Kenobi was killed by Darth Vader on the first Death Star in a duel. Vader swings a strike at the Jedi Master but it seems Obi-Wan allowed him to do this, to show Luke that you can become more powerful when you die. Obi-Wan continued to guide Luke Skywalker in the ways of the force as a Force Spirit.
Alternate Timeline
In an alternate future when Darth Vader was killed by his apprentice Galen Marek, who would then become Darth Sidious' assassin Lord Starkiller, Starkiller was sent to Tatooine to retrieve the Death Star plans placed in R2-D2 after they were stolen by the Rebel Alliance. Starkiller eventually tracked them to the Millennium Falcon but was confronted by Obi Wan - although Starkiller was thrilled at the possibility of finally been able to kill the legendary Jedi.
Despite his old age, Obi Wan proved an experienced and capable combatant - calling a swarm of practice orbs to assist him during the battle and even displaying the ability to use Force Lightning. However, Starkiller's power would prevail in their first duel as he proceeded to impale the elderly Jedi in his shoulder before using the force to throw him into the Falcon's engines.
However, Kenobi reappeared - now as a Force Ghost - and resumed his lightsaber battle with Starkiller before he could enter the Millennium Falcon. However, Starkiller still managed to best Kenobi - defeating him in combat and causing his spirit to disappear with a blast of Force Lightning. Unable to battle Starkiller, Kenobi's spirit told Luke to run, with the Millennium Falcon fleeing Mos Eisley.
Despite his death, Obi-Wan continued to train Luke Skywalker as a Jedi. His efforts would prove futile thought as Starkiller would battle Luke on the ice-world of Hoth - defeating Luke in combat and causing Luke to turn to the Dark Side; becoming Starkiller's apprentice.