I honestly think that the Icebreaker is the most functional exotic to have in PvE Endgame content even if it isn't actually equipped more often than Gjallarhorn, because people use it to refill some of their Special ammo conveniently.
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Red Death for health regen. I have a sniper that gets knights down to a sliver of health on CE. I use that and RD for a guara teed health regen. The vex, because it vaporises enemies in no time at all. 500+ crit damage, at a rate of fire that feels quicker than the Suros, it does over 18k damage per clip...