We see that Finn can fight with a lightsaber, 

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>  first on Takodana against strormtroopers and later on Starkiller base against Ren.
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Is this something that's part of his back story that we're going to find out later, or is there some little-known fact about Stormtroopers that they're trained in hand-to-hand combat with non-projectile weapons? If memory serves, this is the first of the films that shows a stormtrooper brandishing anything besides a blaster-type weapon; as such, there's never been any suggestion that they are trained with other types of weapons.