Jyn is one of the most important characters in Rogue One. Whether you like her character or not doesn’t matter – you cannot deny that she had one of the most important scenes in the entire film. And I’m not talking about her sending the Death Star plans (although that was pretty important). I’m talking about her giving a blaster to K-2SO.
While it may have simply seemed a moment of ‘character development’ for Jyn, that one action probably goes far beyond the relationship between two space-dwellers. K-2SO getting a blaster was just one small step toward droid freedom, a struggle that arose after the end of the Clone Wars.
The last time the Star Wars universe saw a droid with a weapon was then, and there haven’t been any weaponized droids since. Artoo had rocket boosters in ROTS, but they disappear by the time ANH rolls around.
Even by the time of TFA, we get BB-8 with, what, a tiny taser? For a Resistance droid who went on missions with one of the most important pilots? You’d think it’d get a little more protection than that.
But, nope. Because living/sentient beings had given droids weapons before, that was a pretty terrible idea for the galaxy. The Clone Wars were a time of intergalactic turmoil and corruption – it’d be more than easy to blame all of that on the beings who can’t fight back: the droids.
And so, while the Galactic Empire still has use for clones, droids are put on the back burner. Everyday people turn against them (even though all the evilly programmed droids were laid to rest), and they’re never to be trusted again. (To be honest, even Cassian seems to act distant toward K-2SO, often taking his droid for granted.)
That’s why Jyn giving K-2SO a blaster is such a symbolic moment. This is the first step of droid liberation.