I've salvaged countless legendaries without knowing their true potential and then kicked myself for it after. Because of this, I wanted to create a list of items that you should not salvage. I have very limited knowledge and so as more items for various classes are brought up in the comments, I'll add to the list. Please list items that essentialy will help players jump up a torment or sets that are a part of a t6 build. (Also Reddit won't let me skip lines for some reason)
All:
- Ring of Royal Grandeur (Ring)
- Thunderfury (Weapon)
- Stone of Jordan (Ring)
- Illusory Boots (Boots)
- Unity (Ring)
- Cindercoat (Chest)
- Magefist (Gloves)
- Harrington Waistguard (Belt)
- Smoking Thurible (Follower Item)
- Skeleton Key (Follower Item)
- Enchanting Favor (Follower Item)
- Nemesis Bracers (Bracers)
- Rimeheart
- Frostburn
- Furnace (2h Mace)
- shard of hate
- Trag-Ouls Coils (bracer) - for cooldown resetting (inventory swap)
- Ice Climbers (boots) - if you can afford nonset boots in your build, these are amazing
- The Witching Hour - bis belt for most classes
- Andariel's Visage (helm) - can roll up to 20% of any elemental damage type
- Goldwrap
- Elemental Immunity Necks (Amulet)
- gloves of worship
- Tasker and Theo (Gloves)
WD:
- Mask of Jeram (helm/mask)
- The Tall Man's Finger (Ring)
- Starmetal Kukri (Ceremonial Knife)
- Thing of the Deep (Mojo)
- Quetzalcoatl (helm/mask)
- Jade Set (Item set)
- The Sunkeeper (1hand mace) - best in slot for jade build
- Uhkapian Serpent (mojo) - best in slot for jade
- Hwoj Wrap (belt) - good belt for jade, especially for soloing
- The Furnace (2hand mace) - beastly for killing rift bosses as Jade.
- Hexing Pants of mr. yan (pants) - good pants (arguably best in slot) for pet build
- Gift of Silaria (1hand sword) - 5 property weapon; BiS for pets if godly rolls
- Swamp Land Waders (pants) - best in slot for poison builds
- Shukrani’s Triumph (mojo) - inventory swap item for running great distances
- Rhen'ho Flayer
Crusader:
- Gyrfalcon's Foote (Flail)
- Jekangbord (Crusader Shield)
- Fate of the Fell (Flail)
- Akhan Set (Item set)
- Darklight (1H flail)
- Hellskull (Shield)
- Swiftmount (1H flail)
Wizard:
- Mirrorball (+2 rolls only)
- Wand of Woh
- Serpent Sparker
- Vyr Set
- Tal Rasha Set
- Moonlight ward
- Velvet Camaral
Demonhunter:
- danetta's set (2x 1 hand crossbows)
- Calamity (1 hand crossbow)
- Kridershot (bow)
- Marauder's Set
- Bombardier's Rucksack
- Ninth Cirri Satchel
- Emimei's Duffel
- Chanon bolter
Monk:
- Gyana Na Kashu (spirit stone)
- Kekegi's Unbreakable Spirit (spirit stone)
- Thundergod's Vigor
- The Fist of Az'Turrasq
- Inna's Set
- The Eye of the Storm
Barbarian:
- Lut Socks (Boots)
- weight of the earth set
- pride of Cassius
- IK Set