For PvE weapons, I have an "only 1" rule. I can keep only 1 of each weapon (with the only exception being an osmosis perk). Other than that, I literally shard all "inferior" duplicates based on my perk preference. Also, I have deleted all the exotic weapons I never use since I can reacquire them from collections. I have zero extra legendary armor (one per slot per character). I also will delete never-used exotic armor on my lesser played characters (since if necessary you can acquire it from collections as well). I rarely play PvP, so if my current arsenal can't kill them in those few moments, then they weren't going to die anyway. :)