Armors and other apparel:

Apprentice Robes of Amplify [Magic School] - All 'amplify/empower' robes are located in Solshteim, very close to a Standing Stone. Conjuration - Beast, Alteration - Earth, Destruction - Sun, Restoration - Water, Illusion - Wind.
Apprentice Robes of Intuition (Intuitive Magic, Novice spells cost no Magicka) - The Ratway Warrens, Esbern's hideout, under the bed.
Apprentice Robes of Shalidor's Shield (Take X% less attack damage while casting a spell) - Fellglow Keep, Ritual Chamber, on the flor behind one of the book pedestals
Boots of Windfall (3% chance per second to restore X points of Health, Magicka and Stamina) - Dead Man's Respite, On a table in the treasure room you reach after the boss fight.
Circlet of Witches (Soul Harvest, gains X soul energy when a living foe dies, granting the Soul Burst power at 1000 soul energy) - Kolbjorn Barrow, next to the pedestal where Ring of Necromany is.
Dragonplate Helmet of Deep Breath (Chance per second to reduce shout cooldown to 3 seconds) - Skuldafn Temple, near the Word Wall
Dragonscale Armor of Magnetism - Forgotten Valley, at the bottom of the frozen lake, next to the falmer treasure chest. Accessible only after the two dragons attack you and break the ice.
Dwarven Boots of Avoidance (Fortify Speed) - Irkngthand Slave Pens, in a torture room next to a stone table woth many posions and some dwarven weapons on it.
Ebony Armor of the Arena (Siphon Stamina, Absorbs Stamina based on level from enemies within X feet) - Ysgramors Tomb, near the boss chest.
Elven Boots of Rollback (With weapons or spells drawn, jump to return to your location from 4 seconds earlier) - Snow Veil Sanctum, next to the Word Wall.
Elven Boots of Virtue (Unbreakable, take X% less damage from power attacks and bashes) - Forgotten Vale, Inner Sanctum, in a secret room accessible through the Paragon Portal.
Elven Helmet of Knowledge (Increased Experience) - Forgotten Vale, Inner Sanctum, in a secret room accessible through the Paragon Portal.
Elven Helmet of Light (Light) - Darkfall Grotto, next to a treasure chest next to the paragon portal.
Expert Robes of the Elements (Area Drain Magic Resist, Reduces the magic resistance of enemies within X feet by 25%) - Mzulft Aerdome, on the stone table behind the puzzle panel, next to the spell books.
Elven Shield of Protection (Defender) - Darkfall Grotto, next to a treasure chest next to the paragon portal.
Glass Bow of Repulsion (Skyhook - chance to lift the target's feet off the ground, immobilizing it for X seconds) - Forgotten Valley, at the bottom of the frozen lake, next to the falmer treasure chest. Accessible only after the two dragons attack you and break the ice.
Gold Necklace of Synthesis (Recharge Weapons) - Tell Mithryn, on an enchanting table in the staff enchanter room, right next to the Black Book
Hide Bracers of Fortify Power Attacks (Power attacks cost X% less stamina) - Gallows Rock, on a table near boss chest.
Hide Bracers of Fortify Bashing (Bashing deals X% more damage) - Gallows Rock, on a table near boss chest.
Imperial Armor of Anarchy (Influence: Fury, enemy creatures and people within X feet have a chance to attack anything nearby) - Solstheim, Fosrt Frtostmoth, in an ash mound next to the boss chest.
Imperial Armor of Panic (Influence: Fear, enemy creatures and people within X feet have a chance to flee from combat) - Katariah, emperors room, opposite to the entrance.
Iron Dagger of Fragments (Frost Damage Piercing, Black ice deals X points of unresistable frost damage to Health and Stamina) - The chill, in the cage with a long dead prisoner.
Jester's Ring (causes attack damage to fluctuate between one fifth and five times damage) Solitude, Blue Palace, Pelagius Wing, on a bench near the entrance.
Leather Armor of Horsmanship (Take X% less attack damage and deal X% more attack damage while riding a mount) - Black Briar Lodge
Necklace of Alarm - The Ratway, in a large, tubal room with a hay and pelt bed and a cooking pot.
Necklace of Life (Spirit of Life, healing allies is twice as effective) - Forgotten Valley, Inner Sanctum, behind a secret passage you can open with the Ewer.
Necklace of Constellations (Fortify Total Armor) - Forgotten Valley, Inner Sanctum, behind a secret passage you can open with the Ewer.
Necklace of Force (Improved Damage from power attacks and bashes) - Ysgramors Tomb, in a big room with mny sarcophagi, on a large stone table with a mamooth skull on it.
Necklace of Grit (Able to power attack for half damage when out of Stamina.) - Ysgramor's Tomb, behind Ysgramor's Statue.
Necklace of Negation (Negate Magic, Having 150% or more resistance to an element grants immunity) - Tell Mithryn, on an enchanting table in the staff enchanter room, right next to the Black Book
Necklace of Perception - Riften, Ratway, on an alchemy table.
Necklace of Showmanship (Gladiator's Glory, gain gold equal to twice your level when you perform a killmove) - Whiterun, Uthgerd's House.
Necklace of Soul Fusion (Deals damage equal to Magicka to nearby targets when equipped and to you when unequipped) - Heamar's Shame, cage room, ona square table.
Necklace of the Cartographer - Riverwood, Sleeping Giant Inn, Delphine's Secret Room, on a small square table in the corner.
Ring of Addiction (Siphon Magicka) - Labyrinthian, Boss Fight Area, under water near a sunken chest, on the stairs.
Ring of Gold Triptych (Triptych: Attributes, if you have a Fortify Health, Fortify Magicka and Fortify Stamina enchantment, increases Health, Magicka and Stamina by 50 points) - Kagrumez, on a stone table under the Black Bow of Fate.
Ring of Faith (Area Restore Health) - Eldrergream Sanctuary, at the top, where Eldergream is, on a rock, between the roots of a dead tree stump with some Mora Tapinella on it.
Ring of Fortify Potions (extends the duration of your potions) - Blackreach, Sinderions Laboratory, on a shelf to the left of the entry.
Ring of Plunder (Magic Find, X% chance to loot an additional magic item from people you kill) - Goldenglow Estate, second floor, Aringoth's bedroom, on a round table, next to a coinpurse.
Ring of Reach (Touch and location target spells can be cast at any distance) - Mzulft Aerdome, on the stone table behind the puzzle panel, next to the spell books.
Ring of Silver Triptych (Triptich: Resistances, If you have a Resist Fire, Resist Frost and Resist Shock enchantment, grants 25% resistance to fire, frost and shock) - Sky Heaven Temple, armory room, on a table with akaviri katanas and all the weapons.
Ring of the Kraken (Link Health/Magicka, increases Health by one fourth of base Magicka and Magicka by one fourth of base Health) - Temple of Miraak Sanctum, on a sarcophagus in front of the boss chest.
Ring of the Titan (Link Health/Stamina) - Gyldenhul Barrow, Treasury Room
Ring of the Blacksmith (Generate Weapons) - Aetherium Forge, on the stone table where you find materials for crafting at the Aetherium Forge.
Ring of the Forge (Generate Armor) - Aetherium Forge, on the stone table where you find materials for crafting at the Aetherium Forge.
Ring of Voracity (Siphon: Health, absorbs Health based on level from enemies within X feet) - Katariah, Emperor's room, on a table in the middle, the one with a map on it.
Robe of Obliteration (Nova, when you fall below 25% Health, X% chance to release an explosion) - Apocrypha, Waking Dreams, near the Word Wall where you fight dragons before confronting Miraak, on the floor.
Robe of Reclaim Magicka (Enemies slain near you give their remaining Magicka) - Soul Cairn Boneyard Entrance, where you first meet Valerica, next to the alchemy table.
Ring Of Leviathan (Link Magicka/Stamina) - Southfringe Sanctum, on the Enchanting Table in the boss room.
Ring of Souls (Generate Soul Gems, grants a filled soul gem at random intervals) - Kolbjorn Barrow, next to the pedestal where Ring of Arcana is.
Scaled Helmet of Nighteye - Ratway Vaults, on a table with a few coinpurses and two small chests.
Shield of Stability (chance to avoid stagger from power attaks and bashes) - Dustman Cairn, on a stone table in front of the Word Wall, near the boss chest.
Silver Ring of Daggers (Fortify Sneak Attacks) - Volundruud, on a sarcophagus, next to the boss chest.
Stalhrim gauntlets of Philosopher's Stone (Generates X gold per hour) - Gyldenhul Barrow, Treasury Room.
Stalhrim Light Cushioned Boots (Negates all Falling Damage) - Gyldenhul Barrow, Treasury Room.
Stalhrim Light Armor of Imminent Victory (Take up to X% less damage from enemy attacks the further their Health falls below 50%) - Gyldenhul Barrow, Treasury Room.
Stalhrim Light Helmet of Divines (Cheat Death, Take X% less damage from attacks when your Health falls below 25%) - Gyldenhul Barrow, Treasury Room.
Steel Boots of Spurs (Mounts move 30% faster) - Black Briar Lodge.
Steel Shield of Fissures (Quake, When you block an attack, X% chance to stagger nearby enemies) - Forgotten Valley, near the Falmer with Auriel's Shield, next to a chest with a skeleteon on it.
Master Robes of Ritual Protection (Immune to stagger and taking half damage from attacks while casting a ritual spell) - Labyrinthian, the boss fight zone, on the ground near an urn, close to where Morokei first spawns.
Necromancer's Robes of Fortify Minions (Friendly conjured creatures get 25% attack damage and 100 HP) - Volkihar Undercroft, Valerica's Lab, on a table upstairs between alchemy and enchanting tables.
Necklace of Fool's Gold (Grants 25000 gold, but slays you if you can't pay it back upon unequipping) - Gyldenhul Barrow, Treasury Room.
Necklace of King of the Lost (An Immortal ghost fights for you) - Abandoned Prison, on a table in the room full of cages on both sides, next to the key.
Necklace of Mark and Recall (Equip to create a magical mark at your location. Unequip to teleport back to the mark) - Bromjunaar Sanctuary, Labyrinthian, where you put all the priest masks, on a nordic shelf.
Necklace of Peace (Influence: Calm, Enemy creatures and people within X feet have a chance to refuse to fight) - Dead Man's Respite, on a table in the treasure room you reach after the boss fight.
Vampire Armor of Suffocation (Living foes that stay within X feet from you for to long are instantly slain) - Volkihar Castle, Volkihar Cathedral, behind Molag Bal's shrine, on the ground.

Weapons:

Battleaxe of Berserking (Reduces the cost of your power attaks for x seconds, on hit) - Dustman Cairn, on a stone table in front of the Word Wall, near the boss chest.
Blades Sword of Dirges (Resonance, sonic vibrations deal magic damage equal to X% of the target's current Health) - Sky Heaven Temple, armory room, on a table with akaviri katanas and all the weapons.
Daedric Mace of Abaddon (Balefire, deals X magic damage for X seconds or until detonated by a power attack) - Mehrunes Dagon Shrine, on a shelf to the right of Boss Chest.
Daedric Sword of Power Unleashed (Power Surge, x% chance on striking to release your currently selected power) - Apocrypha, Miraak final fight location, on the floor, near the edge of the platform, next to one of the puddles Miraak teleports to during that fight.
Dagger of Battlecries (Deals X shock damage as magic and applies the effect of many equipped shouts) - High Hrothgar sleeping area, on a dresser.
Dwarven Bow of Schock Blasts (Shock Hazard, electrifies the ground underneath the target, dealing X damage for X seconds) - Black Reach, Silent City Catacombs, under water, near the two small dwemer chests.
Dwarven Dagger of Depletion (Discharge, steals targets equipped weapon's charges) - Fahlbtharz Grand Hall, in the final room, right next to the Best Helmet in the game.
Dwarven Dagger of Slow Burning (Fire Damage Lingering, target burns for X points per second until combat ends) - Black Reach, Debate hall, upper level, next to a skeleton.
Dwarven Dagger of Ice Blasts (Frost Hazard, freezes the ground underneath the target, dealing X damage for X seconds) - Black Reach, War Quarters, in a dorm room on one of the stone beds.
Dwarven Sword of Surges (Shock Damage Wild, delivers a X point static shock, 10% chance to deal 5 times damage). - Fahlbtharz Grand Hall, in the final room, right next to the Best Helmet in the game.
Dwarven Mace of Scorching Blasts (Fire Hazard, ignites the ground underneath the target, dealing X damage for X seconds) - Black Reach, Silent Ruin, Behind the large Dwemer Chest.
Dwarven Mace of Seething (Disease Damage) - Bthardamz Arcanex, in the elevetor taking you back to the surface, next to the container.
Dwarven Mace of the Land (Shifting Earth, if the target is staggered, X% chance to summon a spike of rock that flips the target into the air) - Alftand Ruined Tower, next to a dwemer chest on the floor.
Ebony Dagger of Adders (Hidden Serpent, if the target leaves combat within X seconds, halves its remaining Health) - Dawnstar DB Santuary, bedroom, on a chest in front of the double bed.
Ebony Sword of Gore (Killstreak, deals X magic damage, multiplied by 5 on the next hit after this kills a target) - Ysgramors Tomb, near the boss chest.
Ebony Warhammer of Imprisonment (Chance to trap a person in a summoned cage for X seconds) - Markarth, Abandoned House, behind the Altar of Molag Bal.
Elven Dagger of the Coven (Command Deadra) - Rimerock Burrow, right next to the Rueful Axe.
Elven Dagger of Grappling (Steal Weapons) Black Briar Lodge, basement on a lower shelf of the counter with some pots and kettles.
Elven Dagger of Grief (Drain Skills) - Black Briar Lodge, on an end table next to the double bed.
Elven Dagger of Healing (Heal) - Eldergream Sanctuary, under a bridge in the lower section.
Elven Sword of Absorb Armor (Absorbs X points of armor from the target for X seconds) - Riften, Riftweald Manor, in the room where the Bust of the Gray Fox is located, on a table.
Elven Sword of Retribution (Karma, X% chance to reduce the target's Health percentage to yours (if yours is lower) - Forgotten Vale, Inner Sanctum, in a secret room accessible through the Paragon Portal.
Glass Dagger of Absorb Speed (Absorbs X% movement speed from the target for X seconds) - Riften, Riftweald Manor, in the room where the Bust of the Gray Fox is located, on a table.
Glass Dagger of Drain Magic Resist (Reduces magic resistance by X% for X seconds) - Solstheim, Highpoint Tower, under Ildari's bed.
Harkon's Off-hand Sword (!) with Death's Door Enchantment (Reduces the target with x% of health or less to 1 HP) - Volkihar Castle, Volkihar Cathedral, behind Molag Bal's shrine, on the floor.
Glass Sword of Wieght (Illusory Burden, Illusory weight temporarily reduces current Health by a quarter for X seconds) - Ratway Warrens, Esbern's Hideout, behind a dresser.
Iron Dagger of Poison Damage (Inflicts a poison that deals X points of damage for X seconds) - Dark Brotherhood Sanctuary, near the entrance, on a barrel next to the shelf with DB clothes.
Iraon War Axe of Doom - Threshold Death, Living target gets a stacking X point curse for X seconds and is slain when this exceeds its Health. - Reachlif Cave, on the Cannibal's feast table.
Nordic Bow of Blackness (Dim Vision, sneaking is twice as effective against the target for X seconds) - Volundruud, behind a sarcophagus, next to the boss chest.
Nordic Dagger of Grounding (Counterspell, x% chance to interrupt the target's spell, draining a quarter of its Magicka) - The Midden, Atronach forge room on the table.
Nordic Dagger of Incompetence (Clumsy, targets stagger whenever they attempt a power attack within X seconds) - Dawnstar DB Santuary, bedroom, on a chest in front of the double bed.
Nordic Dagger of Insults - Ratway Vaults
Nordic Dagger of Superiority (Momentum, Lowers poise by X% for X seconds and staggers targets with zero poise) - Ratway Vaults.
Nordic Dagger of Threshold Wail - Bloodlet Throne, the boss fight area, behind a bench.
Nordic Greatsword of the Ancients (Rolling Thunder, If the target dies within X seconds, X% chance to refresh your shout cooldown) - Sovnegard, Hall of Valor, near the the huge fireplace in the middle.
Nordic Greatsword of the Graybeards (Beaconbound: High Hrothgar, deals X magic damage while near High Hrothgar) - High Hrothgar, sleeping area, behind a dresser.
Orcish Dagger of Infection (Poison Damage Cumulative, toxins deal a stacking X points of poison damage for X seconds) - Dark Brotherhood Sanctuary, on the alchemy table.
Orcish Dagger of Noise (Sound, chance to create a distracting noise that interrupts spellcasting for X seconds) - The Midden under that weird deadric hand.
Orcish Mace of Hurling (Threshold Throw) - Largashbur Basement, behind the counter.
Stalhrim Axe of Wilting (Halt Regeneration, prevents Magicka and Stamina regeneration for X seconds) - Temple of Miraak Sanctum, on a sarcophagus in front of the boss chest.
Stalhrim Dagger of Crumpling (Drain Armor Rating) - Gyldenhul Barrow, Treasury Room.
Stalhrim Sword of Futility (Drain Damage) - Gyldenhul Barrow, Treasury Room.
Steel Mace of Might (Power Attack Damage, power attacks deal X extra damage) - Driftshade Cellar in the torture chamber with one dead werewolf, on a bloody table.
Steel War Axe of Anger (Battle Hunger, target is consumed by anger, taking x magic damage for X seconds or until it attacks or casts a spell) - Hag's End, in a tent with the large chest, on the table).
Steel Warhammer of Noon (Sun Damage) - Dimhollow Crypt, on a pedestal with two gorgoyles, right behind where Vigilant Adalvald is interrogated.