Usefulness for me, as I level up my cooking and first aid and various characters and alts.

Vendor trash and items I've grown out of

Bear Meat
Two recipes: Blood Sausage (60-100-120-140, recipe bought from Old Town in Stormwind) and Smoked Bear Meat (40-80-100-120, recipe bought from Loch Modan (Thelsamar) or Silverpine Forest (The Sepulcher))
Boar Intestines
Used only in the essentially Alliance-only recipe Blood Sausage, 60-100-120-140. Sells for 18c.
Buzzard Wing
Barbecued Buzzard Wing learnable at 175 and turns grey at 255 (recipe)
Chunk of Boar Meat
Cooked into Roasted Boar Meat, 45-65-85, recipe learned from trainers.
Crisp Spider Meat
Cooked into Redridge Goulash, 100-135-155-175, basically Alliance-only recipe, sold in Stormwind and as a quest reward. Sells for 50c.
Crunchy Spider Leg
A low-level drop added in TBC, can be cooked into Crunchy Spider Surprise, 60-100-120-140, recipe only sold in Ghostlands and Bloodmyst Isle. Sells for 12c.
reagent only for Smelt Steel, sold by Trade Goods vendors for around 5s, sells to vendors for 1s 25c, don't even bother to AH it.
Coarse Gorilla Hair
used in one Leatherworking recipe, skill level 200, hard to sell, nobody cares after TBC came out. Sells to vendors for 6s 8c.
Dampscale Basilisk Eye
only used to grind back Scryer reputation if one went with Aldor and want to switch. Barely worth auctioning. Sells for 6s 76c.
Enchanted Water
has a few uses, but either AH it or just vendor it. Sells for 1s 33c.
Fish Oil
Used only as a reagent for water walking by Shamans. Sells for 7c.
Flask of Big Mojo
some use in three LW and JC recipes between 240300. Sells to vendors for 5s. Probably not worth trying to AH.
Gooey Spider Leg
Cooked into Gooey Spider Cake, 100-150-170-190, recipe only sold in Stormwind.
Gorilla Fang
Objective of the quest Stranglethorn Fever, which needs 10. Not used in any crafting recipe, no other use. Sells for 67c.
Huge Venom Sac
only used for TBC antivenom by Rogues, sells for 15s.
Jaggal Clam Meat
Cooking, one recipe, 300-320-330-340. Sells for 7s.
Large Fang
Used in two Leatherworking recipes (one blue, one green, skill ~150), three Blacksmithing recipes (all green, skill ~180), one Enchanting recipe (skill 175), and one Alchemy recipe (Great Rage Potion, skill 175). AH'able, but hard to sell.
Long Elegant Feather
used only in one Tailoring recipe (Admiral's Hat, which requires six feathers; skill 240285), and in one Horde quest (Another Message For The Wildhammer). Sells for 5s 30c.
Long Tail Feather
used in one Leatherworking recipe, to create supposedly OP hunter gloves, but barely sells in the AH. Sells to vendors for 3s 3c.
Lean Wolf Flank
Two recipes: Lean Wolf Steak (125-165-185-205, recipe bought from the traveling Super-Seller 680 in Desolace), and Seasoned Wolf Kabob (100-140-160-180, recipe bought from Stormwind, or rewarded from an Alliance quest in Duskwood). More trouble than it's worth if you're Horde.
Murloc Eye
The only use is in making Westfall Stew, 75-115-135-155; the recipe is only sold in Stormwind.
Mystery Meat
Cooking, three recipes, two of them (Carrion Surprise, Mystery Stew) 175-215-235-255, the third (Dragonbreath Chili) is 200-225-237-250.
Raptor Egg
Cooked into Curiously Tasty Omelette, 130-170-190-210, recipe sold in Stormwind (Alliance-only) and Arathi Highlands and Stranglethorn Vale (both Horde-only trade goods vendors).
Raptor Flesh
Cooking, Roast Raptor, 175-215-235-255, recipe bought from Desolace (from the traveling Vendor-tron 1000), Arathi Highlands, Dustwallow Marsh and Stranglethorn Vale (faction-specific vendors in all these zones).
Raptor Hide
Used for 3 leatherworking recipes but not worth AHing for like 2s 30c when it vendors for 2s 8c.
Raw Spinefin Halibut
there is no cooking recipe, it's just vendor trash. Sells for 1s 60c.
Red Wolf Meat
Cooking, Hot Wolf Ribs, 175-215-235-255, recipe bought from Super-Seller 680 in Desolace, or faction-specific vendors in Feralas.
Savage Frond
turn in 30 at a time for Argent Dawn reputation and an Insignia of the Dawn. Sells for 2s. Basically vendor trash.
Shiny Fish Scales
used only for Shamans' Water Breathing, marginal AH, Sells for 7c.
Slimy Murloc Scale
Used in two low-level green Leatherworking recipes (around skill level 90). Sells for 75c.
Small Egg
Sells for 4c. Used for low-level cooking (Herb-Baked Egg, learned from trainers, 1-45-65-85. Also used during the Feast of Winter Veil, to make Gingerbread Cookies and Egg Nog, very sought after at this time.
Small Spider Leg
Cooking, Kaldorei Spider Kabob, 10-50-70-90, recipe only obtained as an Alliance quest reward in Teldrassil. Sells for 3c.
Small Venom Sac
Only one use, for the First Aid recipe Anti-Venom, 80-80-115-150, learned from trainers. Sells for 82c. You can make a two copper profit by turning each Small Venom Sac into three Anti-Venom, which sell for 28c each.
Spider Ichor
Cooked into Blood Sausage, 60-100-120-140, recipe only sold in Stormwind
White Spider Meat
Cooking, 200-225-237-250 (only one recipe, Spider Sausage)
Wicked Claw
Used in two recipes: the purple Lionheart Helm, a level 300 blacksmithing recipe, which needs 40; and the blue Wolfshead Helm, a level 225 leatherworking recipe, which needs 8. AH'able, but hard to sell.

Items with some use

Boar Ribs
Two recipes: Dry Pork Ribs (80-120-140-160, requires one + Mild Spices) and Succulent Pork Ribs (110-130-150-170, requires two + Hot Spices)
Core of Earth
reagent in BS and LW recipes, skill level 260-ish, creates items of item level 50. Sells to vendors for 4s.
Core of Elements
only used in two quests, one repeatable; 30 of them are turned in at Light's Hope Chapel for one Insignia of the Dawn. Sells to vendors for 2s.
Deeprock Salt
used in one LW recipe (to create Cured Thick Hide, used in 17 other recipes, so quite wanted), one Cooking recipe and one Engineering recipe. AHs for >17s on the server I'm on. Sells to vendors for 2s 50c.
Elemental Earth
used in a bunch of crafting recipes around skill level 200, creating item level 40-ish items. Sells to vendors for 4s.
Essence of Fire
lots of stuff, Classic end-game recipes and the like.
Flask of Mojo
some use in LW, JC, Engineering, in recipes between 210260ish. Sells to vendors for 2s 50c.
Ghost Mushroom
used in five high-level (250ish) Alchemy recipes.
Giant Egg
the quest Clamlette Surprise, Cooking (1 recipe, Monster Omelet, 225-250-262-275, 1 egg and 2 Soothing Spices per cast)
Heart of the Wild
Tailoring (225, for blue items), Engineering, Alchemy, JC
Large Venom Sac
AH'able. Sells for 1s 85. Used in one Alchemy recipe (Elixir of Poison Resistance, 120-185), Rogues' Instant Toxin spell, and First Aid's Strong Anti-Venom (130-200).
Nightmare Vine
Used for TBC Alchemy, skill level 350-ish onwards. Sells for 12s 50c.
Raptor Ribs
one Cooking recipe, 335-355-365-375
Sandworm Meat
the only meat that can be cooked up to skill level 300, one recipe (Smoked Desert Dumplings), 285-310-322-335, recipe learned from a quest that requires Cooking 285 to pick up from Calandrath, the innkeeper at Cenarion Hold in Silithus. (Take this quest while you farm.)
Shadow Silk
A lot of Tailoring recipes for green items, and two Engineering items. Sells for 10s.
Sharp Claw
Used for two Blacksmithing recipes (green items, skill levels 160 and 175) and one Alchemy recipe (Rage Potion, skill level 60-130). Sells for 45c.
Spider's Silk
Tailoring, three green items and one blue item; one Leatherworking recipe for a blue item.
Solid Stone
also a mining reward, mined from mithril nodes, used in Engineering and Blacksmithing in recipes between 175 and 200 skill level, used to create further reagents or recipe parts, no valuable items. Sometimes easy to sell on the AH, can sell for around 25s each. Sells to vendors for 1s.
Tender Crab Meat
used only in one recipe, Spiced Chili Crab (225-250-262-275, also needs 2 Hot Spices, recipe sold in STV (Uthok at Grom'Gol) or Swamp of Sorrows (Banalash at Stonard) or Westfall (Kriggon Talsone at the very southwestern tip of the mainland))
Tender Wolf Meat
Cooking, one recipe, 225-250-262-275.
Thick Spider's Silk
Four Tailoring recipes, one Gnomish Engineering one (Gnomish Net-o-Matic Projector), one Leatherworking recipe.
Vibrant Plume
used for a neutral Darkmoon Faire quest; turn in five Vibrant Plumes for 12 Darkmoon Faire Prize Tickets.
Zesty Clam Meat
Cooking one recipe (Undermine Clam Chowder), 225-250-262-275. Also needed for the quest Clamlette Surprise, received in Gadgetzan from Dirge Quikcleave, which is the only way to learn Cooking up to level 300. Sells for 50s; the cooked version, Undermine Clam Chowder, sells for 1s, but requires two Clam Meats plus Hot Spices (~40c) and Ice Cold Milk (~1s), so cooking for vending is unprofitable.

All the different fish and the levels they're cooked at

Barbed Gill Trout
Outland fish, found in all Outland outdoor zones, Deadwind Pass, Serpentshrine Cavern, Underbog. Two recipes: Blackened Trout (300-320-330-340, recipe bought from Zangarmarsh) and Stewed Trout (335-335-345-355, recipe bought from barmaid Kylene in Shattrath).
Big-Mouth Clam
Contains Zesty Clam Meat
Bloodfin Catfish
Added in TBC, fished in Deadwind Pass. Cooked into Broiled Bloodfin, 300-320-330-340, the recipe is a green item and is contained in a cooking daily quest reward item.
Darkclaw Lobster
Only fished in Azshara, and according to comments requires a very high fishing level, close to 300. Can be made into Lobster Stew, 275-315-335-355, one of the few recipes that can be used to get to cooking level 300. The recipe can only be bought in Feralas.
Darkshore Grouper
Only fishable in Darkshore. Objective of an Alliance quest that awards a fishing pole. Not used for any recipe, but can be eaten and fed to pets.
Deviate Fish
Reagent for an Alchemy recipe (Elixir of Giant Growth, recipe is a rare drop from The Barrens, 90-120-140-160) and one Cooking recipe (Savory Deviate Delight, also a drop from the Barrens, 85-125-145-165)
Deviate Scale
Not a fish, but fished in the Barrens where Deviate Fish are also fished. Only used for Leatherworking recipes in the 90 to 150 range.
Figluster's Mudfish
Outland fish, fished in Nagrand and Netherstorm. Cooked into Grilled Mudfish, 320-340-350-360, recipe bought from faction-specific vendors in Nagrand.
Firefin Snapper
Only used for the Alchemy recipe (learned from trainers, 130-150-160-170) that creates Fire Oil.
Fish Oil
Also not a fish, but can be fished in Desolace. Used for the Shaman spell Water Walking, otherwise junk.
Furious Crawdad
Outland fish, only fished from a few mountain lakes in Terokkar Forest, accessible only by flying mount. Cooked into Spicy Crawdad, 350-370-380-390, recipe bought from faction-specific vendors in Terokkar Forest.
Golden Darter
Outland fish, fished in Zangarmarsh and Terokkar Forest. Cooked into Golden Fish Sticks, 325-345-355-365, recipe bought from faction-specific vendors in Terokkar Forest.
Icefin Bluefish
Outland fish, fished in Nagrand and Netherstorm. Cooked into Poached Bluefish, 320-340-350-360, recipe bought from faction-specific vendors in Nagrand.
Large Raw Mightfish
Also fished only in Azshara, reagent for Mightfish Steak, another one of the few recipes to get to 300 (275-315-335-355), recipe bought from Feralas.
Lightning Eel
Useless, only used in a turn-in quest in the Eastern Plaguelands (at Light's Hope Chapel), where 30 can be exchanged for an Insignia of either the Crusade or the Dawn.
Oil Covered Fish
Fished in Stonetalon Mountains, in Windshear Crag. No cooking recipe, a very weak food (61 health), sells for 1 copper, vendor trash.
Oily Blackmouth
Reagent for the Alchemy recipe for Blackmouth Oil (80-80-90-100), taught by trainers.
Raw Brilliant Smallfish
One of the first fish fished. Can be cooked into Brilliant Smallfish, 1-45-65-85. The recipe can be bought from Fishing Supplies vendors in Thunder Bluff, Undercity, Stormwind, Dun Morogh, Loch Modan, Mulgore, Elwynn Forest, Teldrassil (cooking supply vendor, Nyoma) and Tirisfal Glades.
Raw Bristle Whisker Catfish
A common low-level fish, fished in zones like Ashenvale, Stranglethorn, Stonetalon, The Barrens, and the capitals (but not Ironforge (except in TBC)). Cooked into Bristle Whisker Catfish, 100-140-160-180, and the recipe can be bought from Cooking and Fishing suppliers in Stormwind, Thunder Bluff, Undercity, Ratchet, and Hillsbrad (both Southshore and Tarren Mill).
Raw Glossy Mightfish
High-level fish. Cooked into (225-265-285-305) Cooked Glossy Mightfish, and the recipe can only be bought from Kelsey Yance, the cook in The Old Port Authority building in Stranglethorn Vale.
Raw Greater Sagefish
Both raw and cooked fish restore mana. Fished in Alterac and Stranglethorn. Cooking skills 175-215-235-255, recipe bought from Cooking Supplies vendors in the capital cities, Micha Yance in Southshore in Hillsbrad, Kelsey Yance in Booty Bay, and a few other places.
Raw Loch Frenzy
Created into Loch Frenzy Delight, 50-90-110-130, recipe bought from Khara Deepwater outside Thelsamar in Loch Modan. Alliance-only.
Raw Longjaw Mud Snapper
One of the most common fish, rivalling Raw Bristle Whisker Catfish. Cooked into Longjaw Mud Snapper, 50-90-110-130, recipe bought from Fishing Supplies vendors in surprisingly few places: Thunder Bluff, Ironforge, Loch Modan, Mulgore, Undercity, Elwynn, Silverpine, Teldrassil.
Raw Mithril Head Trout
Cooked into Mithril Head Trout, 175-215-235-255, recipe sold in Hillsbrad (Alliance only), Stranglethorn (Kelsey Yance), Ironforge, Undercity, Orgrimmar, Wetlands, couple of other places.
Raw Nightfin Snapper
Cooked into Nightfin Soup, 250-290-310-330, recipe bought from Gikkix at Steamwheedle Port in Tanaris.
Raw Rainbow Fin Albacore
Cooked into Rainbow Fin Albacore, 50-90-110-130, recipe bought from many places, fishermen and Fishing Supplies vendors in Stormwind, Orgrimmar, Barrens, Westfall, Wetlands, Teldrassil, Durotar, Undercity, Silverpine.
Raw Redgill
Cooked into Filet of Redgill, 225-265-285-305, recipe only available from Kelsey Yance in the Old Port Authority Building, Booty Bay, Stranglethorn Vale.
Raw Rockscale Cod
Cooked into Rockscale Cod, 175-190-210-230, recipe sold in Stranglethorn Vale (Kelsey Yance, Booty Bay), and fishing suppliers in Ironforge, Undercity, Orgrimmar, Darkshore, Hillsbrad (Southshore, Alliance only), a couple of other zones.
Raw Sagefish
Cooked into Smoked Sagefish, 80-120-140-160, recipe available from quite a few places: Cooking Suppliers in Thunder Bluff, Stormwind, Orgrimmar, Undercity, Ironforge, Darnassus, Shattrath, Silvermoon, Azuremyst Isle, Exodar, and others.
Raw Slitherskin Mackerel
One of the common low-level fish, very ubiquitous, also in drops from water-adjacent mobs. Cooked into Slitherskin Mackerel, 1-45-65-85, but the recipe is available from surprisingly few places, all Fishing Suppliers or Fishermen: Tansy Puddlefizz in Ironforge, Martine Tramblay outside and to the east of the road to Undercity in Tirisfal Glades, Kriggon Talsone at the very southern tip of the shore of Westfall, Zansoa at Sen'Jin Village in Durotar, and finally Nessa Shadowsong at Rut'theran Village in Teldrassil.
Raw Spinefin Halibut
Cannot be fished, only obtained as a drop. Cannot be cooked either: they forgot to put the recipe in. Their only use is as a mediocre food, 1392 health over 30 seconds. Sells for 1s 60c.
Raw Spotted Yellowtail
Cooked into Spotted Yellowtail, 225-265-285-305, recipe bought from Gikkix at Steamwheedle Port in Tanaris.
Raw Summer Bass
A high-level fish. Cooked into Hot Smoked Bass, 240-280-300-320, recipe bought from Kelsey Yance at Booty Bay, Stranglethorn Vale.
Raw Sunscale Salmon
Cooked into Poached Sunscale Salmon, 250-290-310-330, recipe bought from Gikkix at Steamwheedle Port in Tanaris.
Raw Whitescale Salmon
Cooked into Baked Salmon, 275-315-335-355, recipe bought from Feralas.
Sickly Looking Fish
Fished in the Undead zones of Undercity, Tirisfal Glade and Silverpine Forest. Not a reagent for anything, barely worth it as food (restores 30 health over 15 seconds), sells for 1 copper.
Spotted Feltail
Outland fish, fished in Zangarmarsh, Terokkar Forest, Serpentshrine Cavern, Underbog. Cooked into Feltail Delight, 300-320-330-340, recipe bought from Zangarmarsh.
Zangarian Sporefish
Cooked into Blackened Sporefish, 310-330-340-350, recipe bought from a vendor (Juno Dufrain) at Cenarion Refuge in Zangarmarsh.

Tailoring: Azure Silk Pants: requires 4 Bolts of Silk Cloth (=16 ordinary Silk Cloth), 2 Blue Dye (about 1 silver total), and 3 Fine Thread (for about 3 silver total), for a vendor cost of at most 4 silver, plus the cost of the silk. The created item is a good source of Soul Dust when disenchanted, requires Enchanting level 50 to disenchant.

Wowhead search: common & is reagent for ability/profession & sourced from a drop (found 300)

posted 2021-11-18, edited 2022-08-17