I have always found Finn and the use of the lightsaber to be interesting. Back before the casting announcement came out for Star Wars: The Force Awakens, one of the first things we ever heard about John Boyega was that he was at Pinewood and he was practicing with a lightsaber. When the casting announcement hit, it became clear there was truth to that. Then we were told conclusively that Finn is a stormtrooper (although we presented it timidly at first, out of caution) and things got complicated without the full picture. Now we know that Finn is a stormtrooper that goes rogue and for a time is in possession of the Skywalker lightsaber.
Maz insists the saber is meant for Rey. Back at the Resistance base, Maz gives the lightsaber to Leia. I think that moment is pretty telling about Maz herself. It says she isn’t a pirate out for personal gain; she cares about the future. So Maz tells Leia the saber should go to Finn (probably knowing his fate is intertwined with Rey’s), which means the saber will get to the correct person eventually.
When Finn gets the laser sword, he doesn’t just tie it to his jacket and look cool. Once the saber is his, he uses it. Apparently when Finn activates the saber to fight Kylo at the end of the film, it isn’t the first time he’s used it. He gets in a little practice as he, Han Solo, Chewbacca, and his new best friend Rey sneak around the First Order fortress planting charges. There are lots of moments of sneaking around and evading squadrons of stormtroopers and they have to take out a few here and there. During some of those moments, Finn uses the lightsaber on stormtroopers defending the “evil castle.”
In short, Finn gets the saber from Leia and Maz at the Resistance base on the green planet. He uses it against stormtroopers during the First Order Fortress attack. He also uses the lightsaber to cut through some things to dismantle the shield protecting the First Order base. By the end of the film, after dismantling stormtroopers and shields, with a little practice under his belt he uses it against Kylo Ren, but loses the fight and the saber forever.
Is Finn sensitive to the Force? We don’t know. I get the sense that we are going to see anyone can become a Jedi in the Star Wars universe and tap into the mysterious Force as George Lucas says they can but only the Jedi have the time to develop the skills. There is clearly an opportunity left behind for Star Wars: Episode VIII here because Rey leaves to find Luke and takes the lightsaber with her. However, Finn is left with Maz who seems to be rather adept in the ways of the Force herself. The two could potentially form a master/student relationship in between films. I guess the question to ask is if can you be a really great swordsman without the Force in the Star Wars galaxy? The Clone Wars had a few instances where evil men used the laser swords without the Force but they were far from one of the three main characters in a new trilogy. I bet Finn takes that Jedi road but we won’t know he’s taken it in Star Wars: The Force Awakens.