first of all, Black Hammer has no place here, it's a Legendary and all others are Exotics ;) ...as far as Exotic Sniper rifles go, Icebreaker is DEFINITELY the most versatile one for PvE, however Patience & Time is the one i vote The Best Exotic Sniper rifle in the game, it is mainly because of how it handles - it has exactly ZERO recoil and fires VERY fast, meaning you can cahin those Critical hits unlike with the other Exotic sniper rifles ...now, as for Legendary ones, this would be mainly based on the perks they come with, however i would say Efrideet's Spear is one of, if not The Best Legendary Sniper rifle in the game