Hey, I've recently been looking for high impact legendary snipers and found nothing.
So, digging into destiny.wikia I found those two:
http://destiny.wikia.com/wiki/The_Supremacy
http://destiny.wikia.com/wiki/Efrideet%27s_Spear
One is Iron Banner's and the other Queen's Wrath', supposedly screens are from beta.
Just wanted to share this :)
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I had supremacy but dismantled it.