List of Mostly Useless Magic Items

[Gnomes2169]

Bucket of really, really old cheese: No seriously, it's that old. Yes, it is a liquid. No, you don't want to touch it.

Weird purple liquid: Tastes oddly like fermented grapes... And gives you blue hair. And when you die, you turn into more of the stuff. So you probably just drank someone, you sick, sick individual you...

Flubber: The only super hero more worthless than aquaman.

A living Remorhaze: Why are you reading this instead of running?

Your mom's dream journal: A cursed item that tells you all of the naughty dreams your mother ever had... In graphic detail and with pictures. You cannot put it down until you read the last page, and every page before it.

Shoes of sogginess: They sort of squelch whenever you take a step... It's kinda gross dude.

The Toupe of Tilting: It just never sits on your head in a natural position.

[Mrmox42]

The Red Shirt: The wearer is sure to die horribly and forces the opponents to cackle in an evil way while it happens.

Cursed Rod of Incontinence: ‘nuff said

The Ring of Secret Invisibility: This ring cause you to turn invisible, but only when nobody’s looking.

Cursed Shoelaces of Untying: Bloody annoying.

The Sausage Sword: This extremely powerful +3 magic sword is cursed to look just like a 4 foot long, tasty sausage, making the wielder look very silly indeed. The Sausage Sword does therefore give a whopping -10 on Intimidation checks, as nobody can take a guy who swings a sausage seriously.

Yo-yo of slightly improved coolness: Causes the wielder to gain the respect of rootless teenagers.

Golf Socks: Has 18 holes.

[Eldan]

Gorilla Glass- This elegant looking wineglass does nothing unusual until it is filled with liquid and someone attempts to drink from it. The drinker must make a dc15 dex save or take 8d6 bludgeoning damage when the liquid turns into an enraged adult gorilla mid-sip. The gorilla tries to kill the drinker until one of them is slain, at which point the gorilla evaporates.

That's not useless. THat makes for an awesome assassination attempt at a banquet.

[JAL_1138]

That's not useless. THat makes for an awesome assassination attempt at a banquet.

Mostly useless =/= entirely useless.

[Unseenmal]

Ring of Doom: Allows the wearer to discern the location of any enemies hidden behind secret doors or walls. However, the only way to discover hidden foes is by knocking on every surface of the room to the tune of "Shave and haircut" until the enemy is compelled to finish it.

I have nothing to add at the moment. I'm just posting here just to acknowledge this awesomeness.

Rubik Gate - A Rubiks cube that when solved makes you feel clever, it may also open a gateway to hell, but you solved the puzzle, so whatever.

I believe you are thinking of the Lament Configuration from Hellraiser

[Epoch]

I'd alter that to Sword of Soap Opera; causes resurrection of random NPCs from two or more campaigns back, plus everyone is immediately related in some way.

Rod Of Studio Set; that fortress, why does the wall wobble when the door shuts?

Oh man, that's great. I'm just picturing a world of TV-themed magic items.

KiltieMacPipes: I'm sad because that was probably the best pun I will ever come up with.

Unseenmal: I appreciate you on a deep level for getting that reference.

[Submortimer]

Cloak of Dramatic Billowing: makes anyone look heroic (optional +1 charm), but a downright liability when you're trying to sneak up on people

My Battlemaster wants this in the absolute WORST way.

[JAL_1138]

Based on the "apprentice on Friday afternoon" scenario of the OP for lazily-designed items...

Trapfinder of the Ancients: an enchanted 10ft pole that is unusually resistant to damage and grants a bonus to trapfinding attempts, but cannot be used with a Thievery, Investigation, or Perception check--the search must be roleplayed out instead, or else it does nothing. Regenerates from damage at 1' per hour from the largest piece left of it if damaged or broken.

Green Slime Remover (Consumable): A very combustible 10ft pole coated in a strange reddish substance--will burst into flame (becoming consumed in the process) at the slightest spark, whether from a candle or a fire spell or a stray piece of cigar ash. When the green slime starts eating it, set it on fire. Deals 4d6 damage to anyone holding it and in a 10' radius of such person if it is accidentally set off, or set off by an enemy.

Vault-Pole of the Ancients: An enchanted 10ft pole that grants advantage on Athletics checks made to pole-vault with it.

Balance of the Ancients: An enchanted 10ft pole that grants advantage on Acrobatics checks when walking on narrow surfaces, but the player must clearly state that they are using the 10ft pole in such manner, or it imposes disadvantage.

Water-Carrier of the Ancients: An enchanted 10ft pole that can be used to carry two buckets (buckets sold separately) of water or other liquid without spilling a drop, regardless of what else is occurring and whether or not it should be physically possible, until set down. This does not prevent the character from falling, being tripped, etc., only prevents the liquid from spilling.

Cubefinder (Consumable): A 10ft pole with one end capped by a caked-on powdery substance. When you are holding it in front of you and feel it hit something unseen, look at the cap. If you see and hear the cap fizzing like crazy while the pole starts to dissolve, you've found a gelatinous cube.

Rustbane: An enchanted (+0) oaken 10ft pole, crudely sharpened at one end as if done in a great hurry with a dull hatchet or light sword. There is a dark stain on the sharp end that extends about a foot back from the point. Counts as a pike, but does half damage (rounded down).

[Zyzzyva]

On the "lacking quality control" front:

Boots of Speed: Enchantment to keep user's pelvis intact while the boots are running is faulty.
Potion of Barkskin: Side effects may include dry, flaky skin, photosynthesis, fruiting.
Deck of Many Things: Contains only 21 cards. Manufacturer will provide refund if told which card, precisely, is missing.
Tome of Clear Thought: Unproofed early edition.
Hand, Eye of Vecna: Corpse items were harvested from not actually Vecna.

[Shining Wrath]

In honor of Gnometown, hats!

Hat of Not a Rabbit: Similar to a Bag of Many Things, you may reach into the hat and pull out just about any Beast in the MM - but never a rabbit. Saying "This time for sure!" has no effect.

Hat of Odd Jobs: Requires attunement, then is a +1 thrown weapon doing 1D6 damage but it ignores all resistance.

Old Silk Hat: Reduces the time required to craft a Simulacrum by 1 minute, then disappears. But it'll be back again someday.

[flakjkt]

Sword of chubby chasing,

1d 20 times per day lude sexual comments are made out loud to any portly female or male characters at random.

[comk59]

Dolphins are highly intelligent sentient beings with communication skills! You cannot eat them!! But that many brilliant sea creatures can make scouring the infinite depths of the seas for something quite a bit easier. Summoning 4d20 dolphins is what you do if you need to find sunken treasure, lost ships, or sahaugin cities.

They might be good at scouting, but you have no control over them, and dolphins are well known *****.

Mat of the Insufferably Flexible: this rubberized flexible mat is brightly colored. When the user utters the command phrase and spends half an hour performing the appropriate ritual, they gain a +2 bonus to all dexterity checks for 24 hours. However, they must constantly tell everyone around them how amazing it is and that they just simply have to try it.

[Submortimer]

Mat of the Insufferably Flexible: this rubberized flexible mat is brightly colored. When the user utters the command phrase and spends half an hour performing the appropriate ritual, they gain a +2 bonus to all dexterity checks for 24 hours. However, they must constantly tell everyone around them how amazing it is and that they just simply have to try it.

To go along with that...

Bar of EXTREME CROSS TRAINING: this heavy, knurled steel bar is 3' long. When the user utters the command phrase, the bar will extend and affix itself to two points on opposing walls. The bar can easily support the users weight, and after spending a half hour performing the appropriate ritual (Pull ups), they gain a +2 bonus to all strength checks for 24 hours. The are compelled to tell everyone they meet about their new awesome training regimen and how its the only way to properly get fit.

[supergoji18]

I cannot claim credit for this, but it just has to be stated:

The Head of Vecna: I think you all know where this is going.

[MadBear]

A Pen of Peter Jackson Scriptwriting: Allows you to see the DM's notes and completely rewrite his plot to add more romance while removing logical coherency

You crack me up sir

[Kurald Galain]

Invisible Ring: Good luck finding it!

And don't forget the classic
Ring of Spell 'Turning' - when activated, it loudly pronounces the letters T-U-R-N-I-N-G.

[Icewraith]

Ring of Spill Turning:

Free flowing liquids reverse direction in a 5' radius from you. Niche use in avoiding boiling oil during a siege or causing minor flow disruptions in very narrow rivers, also causes anything spilled AWAY from you to change course back at you.

[Totema]

Those 4D20 dolphins could be very useful for some hungry people.

4d20 dolphins... Hungry people... Nah. Too easy.

[Shining Wrath]

You crack me up sir

Thank you, I'll be here all week, try the dolphin veal.

[MadBear]

Ring of Bullywug moistness: You permanently gain the moist condition. It has not status effect, but on the flip side you're moist...... forever..........

[Shining Wrath]

Amulet of Cleavage When worn over any garment or armor, nicely accentuates your pectoral muscles or mammary equipment. Otherwise useless.

Grand Piano of Courage Allows any bard who moves at least 10 feet on their turn while carrying the GPoC to grant Inspiration to one ally.

[xyianth]

My contribution to this wonderful thread:

Periapt of Wisdom: Whenever you fail a knowledge check, you are instantly reminded that you failed it. You are, after all, wise enough to know how dumb you are.
Ring of Cartoon Physics: You are immune to gravity, until someone points it out or draws attention to it.
Boots of Teleportation: 1/long rest you can activate these boots. These boots (and only the boots) teleport to the location you specify as if using the word of recall spell.
Psychic Paper: This small slip of paper appears to have whatever the viewer is thinking about written upon it. Upon closer inspection, the writing changes to depict the viewer's best kept secret. The writing is unique to the viewer, no one can read what it displays for someone else.

[Mrmox42]

The Head of Vecna: I think you all know where this is going.

Oh yes. This one brings back good memories.

[Knaight]

A lot of dumb fad products aimed at children transfer over surprisingly well:

Broach of Color Changing - A cheap trinket sold for the novelty of a broach that changes color based on your emotional state, allowing for analysis therein. It actually changes color based on ambient temperature.

Miniature Goo - A fist sized blob of grey goo, alleged to learn to fit it's master, designed as an alternative to standard familiars. It actually displays the same bad approximation of intelligence regardless and is incapable of learning.

Then there's quality control:

Stiffening Mail - This set of mail is extremely flexible and minimally hindering, but hardens when struck to defend against blows as well as plate. Unfortunately, it also hardens when brushed against particularly hard, when the wearer moves too suddenly, or if it is exposed to a particularly potent gust of wind.

Robe of Swimming - This intricate blue robe of heavy fabric, embroidered with gold thread in the pattern of waves on a sea is enchanted to help it's wearer swim. It's also heavy, dense, extremely water absorbent, and prone to dragging in the water. The enchantment almost completely counteracts the obstacle the robe itself presents to swimming.

Bottle of Endless Wine - A delicate looking crystal bottle, the bottle of endless wine always seems to be full, yet still pours out wine at a normal rate. The enchantment is extremely well made, the bottle itself is magically reinforced and well crafted, and the wine it pours may or may not actually be vinegar.

Rope of Pulling - At first glance, the rope of pulling looks like a normal silk rope. There's a knot near the middle of it however, which sticks to surfaces and lets the rest of the rope slide through, allowing it to act as a pulley. It doesn't stick well enough to surfaces to stay on when supporting any weight actually worth using a pulley to move.

[Mrmox42]

Wand of Turning Undead Spins the undead 180 degrees around.

[Cazero]

Wand of wand recursion
Creates a wand. The wand turns to dust upon use. The created wand can only be used to create a wand, and turns to dust upon use. The wand createed by the created wand...

[Azarin921]

Blade of Death: Anytime this mystical sword is drawn, it immediately kills the wielder and re-sheathes itself. Nothing can bring the wielder back to life.

[JAL_1138]

Gnomish Automatic Beard-Trimming Machine: Last time it escaped, it killed ten men

[comk59]

Amulet of Phasing: This plain silver medallion is on a thin chain. When the command word is spoken, the wearer will be able to pass through any matter and force effect, and ignore any magical movement effects that would normally apply to them, such as fly or hold person. It does not, unfortunately, let the wearer ignore gravity.

[Talderas]

Amulet of Phasing: This plain silver medallion is on a thin chain. When the command word is spoken, the wearer will be able to pass through any matter and force effect, and ignore any magical movement effects that would normally apply to them, such as fly or hold person. It does not, unfortunately, let the wearer ignore gravity.

Wand of Bark When used the wand summons a small pile of tree bark.
Wand of Bark When used the wand makes an audible noise that sounds like the bark of a dog.