Here are some magic items that have made an appearance in some of my gaming recently. They're designed for D&D 5e (because that's the game we were playing at the time), but can be used in TSR-era D&D with little tweaking.
Swish
Swish is a +1 swept-hilt rapier with a blade fashioned from gleaming mithril and tower engraved on the pommel. For every opponent personally attacking the wielder of Swish beyond the first, Swish grants its wielder a +1 to AC up to a max of +5.
The Lady
The Lady, so the joke goes, is disarming. Swish is a +1 rapier with a silvered blade, orichalcum swept hilt and pommel, and an ivory grip. Whenever the wielder of the Lady makes a successful attack with her, the wielder can choose to forgo doing any damage and instead attempt to disarm the person they attacked. The target must roll a Strength save with a DC of the wielder of Lady’s spell save DC (or their Dexterity bonus + 8 + their proficiency bonus if they don’t have a spell save DC) in order to keep their grip on the weapon. Otherwise, it is tossed 5d4 feet away from the wielder in a random direction.
Polydipsia
Powers
Polydipsia is a +1 longsword that thirsts for blood. In addition to its usual +1 to attack and damage rolls, when used against a living creature with internal fluids (blood, ichor, etc.), the blade does an additional 1d4 necrotic damage as it sucks these fluids into itself. Against constructs, most undead, and other creatures that lack internal fluids, it simply works as a normal longsword +1
If Polydipsia is ever sheathed without drinking blood, it will bite whoever sheathed it for 1d4 necrotic damage.
If Polydipsia ever deals the finishing blow on a creature it can drink from, it gorges itself on the creature’s fluids. Until the wielder’s next long rest, it acquires an additional +1 to attack and damage rolls. The DM may decide that gorging this way on particular creatures (angels, demons, mindflayers, etc.) might grant the wielder additional, one-use powers.
If the wielder of Polydipsia gets into a heated confrontation, the blade will murmur and whine thirstily. If Polydipsia’s wielder gets into a fight but doesn’t draw Polydipsia, the wielder must pass a CR 12 Charisma saving throw or use the blade to deadly effect. Some of Polydipsia’s wielders have taken to chaining the sword in her sheath. While chained, while Polydipsia can’t force her user to wield her, she will rattle and hiss. (Chaining the sword in its sheath requires a full action to get Polydipsia free.)
Polydipsia cannot be used to deal non-lethal damage. Wielding Polydipsia while she is still chained in her sheath will allow for non-lethal damage, but she’s treated as a club and her magical powers are negated until she is free of the sheath.
Description
Polydipsia looks like an elegant longsword with graceful cross guards that curve gently towards the sword’s point and set with small, smokey garnets between the grip and the blade. The octagonal pommel is decorated with obsidian plates and the grip is wrapped in shark skin.
The ricasso has two thorn-like projections in line with the edge of the blade. The ricasso also bears a maker’s mark, identifying it as the work of a particularly skilled but mad swordsmith. The blade itself is delicately engraved with a roses-and-thorns pattern.
The Mask of Falier
Powers
While carried, the Mask of Falier allows the bearer to cast the Minor Illusion, Prestidigitation, and Thaumaturgy cantrips.
While worn, in addition to the above powers, the mask confers the following benefits on the wearer:
Targets of Vicious Mockery had disadvantage on their saving throws against it.
The wearer can cast Alter Self on themselves once per hour.
The wearer can cast Blur once per day, the power recharging at dawn.
The wearer has advantage on Deception, Intimidation, and Sleight-of-hand skill checks.
The wearer has advantage when resisting any sort of gaze attack or magic, such as the gaze of a vampire or medusa.
Description
The mask has the ability to transform itself into any shape the wearer desires, but it must remain a mask. It always looks like a mask, so while it can form itself into a caricature of a known person, it cannot imitate their exact look. The mask is immune to mundane damage.
Exactly who Falier is has bedeviled generations of historians. Some say Falier was one of the nomes de guerre of the half-elven illusion most commonly known as Kmikle. Others claim Falier is the true name of a demon who is bound inside the mask.