I haven't read any of the other recommendations, so these may be duplicative, but hopefully there are some new ideas here.
To help encourage consumables:
Balder's Goblet: Double the healing from a potion, once per room. Slotless
Goggles of Tyr: Double the damage from a common or uncommon damage scroll, once per room.
Loki's Gloves of Chaos: Double the damage of all ammunition
Others:
Brísingamen (neck slot): Grants +4 Fire Damage to all weapon attacks, prevents 10 fire damage to wearer
Freya's Cloak (image should show cloak made of Falcon Feathers): +2 to Saves, -5 from all Ranged Attacks
Balmung: +2 Sword, slays Dragon on a natural "20" if the top damage symbol is slid.
Bodn (slotless container): Drinking from it in the training room gives a clue to the Dungeon.
Draupnir (Ring Finger Slot): Successful Melee attack on one monster does 1/2 damage to up to two other monsters
Dromi (weapon): Successful hit on monster "binds" it for one round, preventing any monster attacks the monster's next round. Once per room (for party).
Widseth's Freyr Sword (in honor of Widseth's Dancing Sword): Bard only, Fights on it's own for 1 room per Dungeon, allowing wielder to take any other non-combat actions.
Gjallarhorn, ‘Hollering Horn’ (slotless) gives the rest of the part +1 to hit and damage for the round it is blown. Can be blown every round. Multiple Horns can be blown each round and are stackable.
Gridarvölr, +2 Staff, slays a Giant on a Natural "20" if the top damage icon is slid.
Megingjörd (waist slot), +2 Strength, +3 Force Damage on Melee attacks
Vidar’s Boot (Feet slot): Prevent all damage from one melee attack, once per Dungeon.