Alchemy:
While some potions have straightforward stat increases like Potion of Spectral Strength, a number of potions in Shadowlands have enhanced effects if your weapon is coated with oil. These two oils, Embalmer's Oil and Shadowcore Oil, are also crafted by Alchemists and feel like a throwback to Classic-era consumables like Wizard Oil.
Potion of Empowered Exorcisms: Your damaging spells and abilities have a chance erupt your target's anima, dealing X Shadow damage to all enemies within 10 yards of the target. If you consume this potion while your weapon is augmented with Shadowcore Oil, the additional damage and range is increased by 20%. Lasts 25 sec. (1 Min Cooldown)
Potion of Deathly Fixation: Your damaging spells and abilities have a chance to apply Deathly Fixation to your target, dealing 185 Shadow damage over 8 sec and stacking up to 5 times. Upon reaching 5 stacks, Deathly Fixation explodes, dealing 7406 Shadow damage to the target. If you consume this potion while your weapon is augmented with Shadowcore Oil, the explosion damage is increased by 10%. Lasts 25 sec. (1 Min Cooldown)
Potion of Divine Awakening: Your healing spells are increased by up to 0, based on the target's missing health. If you consume this potion while your weapon is augmented with Embalmer's Oil, the additional healing is increased by 10%. Lasts 25 sec. (1 Min Cooldown)
Potion of Phantom Fire: Your attacks and spells have a chance to send out a fiery projection at your target dealing 0 Fire and Shadow damage. If you consume this potion while your weapon is augmented with Shadowcore Oil, the additional damage is increased by 10%. Lasts 25 sec. (1 Min Cooldown)

Potion of Sacrificial Anima: Your next 4 mana consuming spells or abilities will consume 7% of your health instead of using mana. If you consume this potion while your weapon is augmented with Embalmer's Oil, the amount of health consumed is decreased by 2%. Lasts 25 secs. (1 Min Cooldown)

There's also a special reagent, Alchemist's Pouch, that increases the duration of your Flask.
Blacksmithing

In addition to crafting the usual weapons and armor, including possible legendary armor, Blacksmiths can once again craft sharpening stones! These feel like a throwback to the popular Elemental Sharpening Stones in Classic WoW.
Grim Iron Shackles
Shaded Weightstone
Porous Weightstone
Shaded Sharpening Stone
Porous Sharpening Stone

Cooking:

In addition to the usual food and feasts that buff stats, each zone has a special type of food with an unconventional buff and additional benefit to members of that covenant:
zzOldArdenweald Zonewich: Restores 51884 health and 83012 mana over 20 sec. Must remain seated while eating. If you spend at least 10 seconds eating you will become Well Fed, granting you move speed for 10 sec when you are near a Beast while in Ardenweald. Members of the Night Fae Covenant again the movement speed if they are near a slain Beast.
zzOldBastion Zonewich: Restores 51884 health and 83012 mana over 20 sec. Must remain seated while eating. If you spend at least 10 seconds eating you will become Well Fed, causing you to automatically levitate while in Bastion. Members of the Kyrian Covenant can glide while falling.
zzOldMaldraxxus Zonewich: Restores 51884 health and 83012 mana over 20 sec. Must remain seated while eating. If you spend at least 10 seconds eating you will become well fed and gain a bonus while in Maldraxxus. Effect increased for members of the Necrolord Covenant.
zzOldRevendreth Zonewich: Restores 51884 health and 83012 mana over 20 sec. Must remain seated while eating. If you spend at least 10 seconds eating you will become well fed and gain 21 Leech for 1 hour.
There are also some interesting utility foods:
Smothered Shank: Restores 51884 health and 0 mana over 20 sec. Must remain seated while eating. If you spend at least 10 seconds eating you will become Well Fed causing you to periodically belch, dealing 500 Nature damage to enemies in front of you.
Seraph Tenders: Restores 51884 health and 0 mana over 20 sec. Must remain seated while eating. If you spend at least 10 seconds eating you will become Well Fed and while out of combat heal for 3250 every 5 sec for 1 hour.
Fried Bonefish: Restores 51884 health and 0 mana over 20 sec. Must remain seated while eating. If you spend at least 10 seconds eating you will become Well Fed and gain Speed for a short time after killing an enemy.

Enchants:

Enchants in BFA were placed on a limited number of slots in contrast to Classic, and now in Shadowlands, it seems that we can once again enchant many types of gear. For example
Chest - Sacred Stats
Cloak - Fortified Avoidance
Boots - Agile Soulwalker
Bracers - Eternal Intellect
Gloves - Eternal Strength
There are even some enchants with creative procs like Eternal Skirmish - Permanently enchants your chest to increase your Strength or Agility by $ec1 and give your auto-attacks and auto-shots a chance to deal additional shadow damage.

As usual, there are new weapon enchants:
Sinful Revelation: Permanently enchants a weapon to allow your offensive spells and abilities to apply a debuff to your target, increasing the damage they take from the damage school associated with the triggering spell or ability.
Ascended Vigor: Permanently enchants a weapon to sometimes increase your healing received when taking damage.
Celestial Guidance: Permanently enchants a weapon to sometimes increase your $pri when attacking, or using spells and abilities.
Eternal Grace: Permanently enchants a weapon to send out a wave of healing energy in all directions from the caster when casting healing spells and abilities.
Lightless Force: Permanently enchants a weapon to have a chance to send out a wave of Shadow energy in front of you when using offensive spells and abilities.
Sinful Revelation: Permanently enchants a weapon to allow your offensive spells and abilities to apply a debuff to your target, increasing the damage they take from the damage school associated with the triggering spell or ability.
Enchanters can also make top-tier reagents for other professions: Enchanted Desolate Leather, Enchanted Lightless Silk, Enchanted Desolate Leather.

Engineers
Engineers always have fun gadgets and Shadowlans is no exception, with items such as:
Holy Hand Grenade of Ardenweald
Momentum Redistributor Boots
Shadow Land Mine
Disposable Ectoplasmic Specs
Wormhole Generator: Shadowlands
There are also belt enhancements for Engineers:
Damage Retaliator: Permanently attach a device to your belt that, when activated, magnetically suspends several small bladed weapons around you, causing any attackers to take damage.
Dimensional Shifter: Permanently attaches a specialized device to your belt, allowing you to attempt to turn invisible while out of combat.
Electro-Jump: Permanently attaches a miniature wormhole generator to your belt, allowing you to instantaneously teleport a short distance.
There also seems to be a greater emphasis on Engineers crafting their unique reagents and parts, similar to older expansions, with items such as Mortal Coiled Spring and Handful of Laestrite Bolts.

Jewelcrafters

In addition to crafting the usual gems, necks, and rings, Jewelcrafters can create enhanced gems such as Quick Jewel Cluster, Deadly Jewel Cluster , Versatile Jewel Cluster and Masterful Jewel Cluster which serve as an Optional Crafting Reagent. This type of material guarantees your crafted item will have a particular stat.

Leatherworking
In addition to crafting Leather and Mail items, including some legendaries, leatherworkers once again have drums, Drums of Deathly Ferocity, but they will not be as strong as drums from the past.
Leatherworkers can also create Stamina kits, Heavy Desolate Armor Kit and Desolate Armor Kit, which feel like a throwback to the armor kits of Classic.