(The part where I add value: some cursed items for your consideration)
The Libram of the Scarlet Fish
This ancient tome is a clear set of instructions usable by any magic-user that will allow them to inscribe the fabled, lost, second-level spell Scarlet Flash, which blinds any number of onlookers for 1d6 rounds when cast. This requires one week of time and at least 1,000 gp worth of supplies, assistants, library access, etc. The book is heavily bound in goat skin, wood, and brass, and features a small illuminated red fish in the margin of every page. Only after full study of the book and following the instructions will the magic-user realize the book is a clever, magical forgery. Once realization dawns the book disappears in a blinding scarlet flash… The magic-user has lost 1,000 gp but gains 250 experience points and will recognize similar books in the future (the author has created several similar volumes).
Ring of Insistent Protection
This ring appears as a boiled leather band, dyed blood-red and set with a small silver shield. It confers protection +2 on the wearer as an extra suit of leather armor until the bearer is attacked by an enemy. At that point it rigidly enforces its standard of protection (AC8: no more, no less), causing any other armor or shielding to fall apart and drop off. Chain mail is reduced to a useless pile of rings, plate will (loudly!) collapse into a pile of unconnected metal pieces, straps fall off shields, armor-like spells (shield, armor, bless, etc.) are dispelled, and other protective magic items must save vs. magic or drop from the bearer. Note that an otherwise unarmored wearer will suffer no ill-effects. Once the ring’s protection has been triggered by attack it can only be removed by purposeful application of 1 hp of the wearer’s blood (which it will soak up like a sponge), or remove curse.
Potion of Vulnerability
This potion grants the imbiber an air of vulnerability by subtly projecting their physical intentions and movement. The user gains +1 to reaction roles involving surrender, but has -2 to AC, is impossible to hide, and will automatically lose any games of skill attempted. These potions are referred to as “gambler’s bane” in legends.
Helm of the Torchbearer
This magical helm is fearsome in appearance, featuring engraved flames of copper and a tightly woven metal face-grill. When worn it constantly projects magical light akin to a bright lantern 30′ in all directions; this is a great boon to the bearer’s companions. The person wearing the helm can see only dimly 10′ and likely needs to be guided. The helm can be removed only at noon, on a sunny day, with the sun shining directly down upon it. Casting light on the helm will extinguish the light for the duration of the spell. Likewise, darkness cast on the helm causes the helm to be blindingly brilliant and illuminate out to 100′ until expiration. Note: no NPC would willingly wear such an item.
Blade of the Specialist
This sword is made of obviously ancient but well-preserved pitted iron and features several small green gems embedded in the pommel. It is otherwise plain and made for use, not for show. Fighters will know on sight it is an extraordinary weapon. It has the following powers: +1 to hit and damage, adopts the alignment of its owner, detects pit traps within 40′ (the bearer gets the repeated sense of falling), and removes all other weapons from its owner. The sword has an intelligence of 6 (no ego). Once used in combat the sword will cause its owner to be unable to hold or even carry another weapon for any length of time; attempts confusingly lead to the weapon being found a few feet away on the ground, in someone else’s pack, hanging on a nearby peg, etc. Can only be removed with remove curse or by pouring a potion of heroism along the blade.
Circlet of the Watcher
A light circlet of silver made to look like an olive branch crown. On close inspection each leaf features an engraved eye. As soon as the circlet is placed on someone’s head, the crown will say, “We’re watching you…” After this the circlet will periodically emit comments about what is going on around it. The wearer cannot be surprised, as the crown will yell first (e.g., “Watch out! Goblins around the corner!”). In every encounter roll a separate reaction roll for the circlet. On a 2-3, the crown will attempt to warn or goad the character’s opponent; on a 11-12, the crown will make some comment (advice, etc.) to aid the character. Once worn the crown may only be removed with a remove curse, facing the gaze of a medusa or basilisk, or by casting clairvoyance on the crown.
Hat of Misunderstandings
This ornate, tiered silk hat features crystals and pearls sewn into intricate patterns. It is clearly meant to be worn at court. Close examination will reveal a small smatter of bloodstains. The hat allows the wearer to understand all languages (as comprehend languages). For languages the wearer knows, the hat renders a perfect translation. If the wearer is hearing or speaking an unknown language however, the hat mistranslates. When relying on the hat for translation make a reaction roll. On a 9-12 the hat translates the spirit of the what is being said. On a roll of 6-8, the message is garbled and nonsensical. On a roll of 2-5 the translation is rendered as a deadly and personal insult. One worn the hat can only be removed by casting friends or remove curse.
(The part where I indulge in thinking about cursed items)
Cursed magical items are an important feature in D&D: a reminder that magic is capricious and dangerous, as a form of trap or trick, and by adding more risk and meaning when magic is found (who dares to use it?). In Moldvay roughly one in eight magic items found will be cursed, enough to make anyone cautious.
Many of the default cursed items have two faults. First, like many other magic items they can be boring. Like a Sword +1, they are a simple expression of game mechanics instead of a unique, coveted treasure. A Sword -1 adds nothing but the knowledge that your character is worse at melee now.
Second, especially before remove curse becomes readily available at sixth level, they can be arbitrarily crippling or lethal and in this way remove some of the joy of playing. I prefer to find a way to ratchet up tension without turning magic into a save or die situation (e.g., poison potions or cursed scrolls, where simply looking at it or tasting it can kill you).
Boring is simple to remedy: cursed items benefit from detail in the same way that “Norfer’s Tooth, a spear that vibrates any time hobgoblins are within half a league, features an obsidian leaf-blade attached to a heavy ironwood shaft wrapped in sharkskin, and is +1 to hit” is more likely to get a player excited than a Spear +1.
Arbitrarily crippling is harder: watering them down is one common way of doing this, like a poison potion that causes disability, sleep, etc. instead of death. Another is presenting tradeoffs where the player can choose to put up with the curse for some benefit. A third is presenting an available solution to remove curse so lower level characters have the ability to get rid of the item without having to track down an NPC cleric.