With Bungie you never know if it's actually a key to a Easter egg.
The Stranger hands it to you. This could be Bungie's way of saying this is important for other things.
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Plus (someone may have said this already) it is pretty much a game changer when you have made a new character for the level 16-20 bit, its got to be the best primary level 16-20s can carry for PVE (as well as pvp). I had played as 3 titans and recently deleted 2 for my warlock and then hunter. Every time, as soon as they hit 16, give them strangers rifle. Compared to whatever white or green scout or handcannon they had been weilding, strangers rifle is a massive step up