I’m running a magic shop based game and I need some items, preferably ones that I could make goofy and contrived quests for. 

Are you saying that you want to have a campaign or part of a campaign based around a shop keeper sending the party out to find wierd magic items?

That sounds pretty cool.

Sunglasses at Night - They allow the wearer to see in the dark. It's because when worn the glasses create magical light that dispels darkness.

Candy Canes - They can provide nourishment for a day or you can suck on them to create a dagger that lasts an hour.

Scroll of Invisibility - It's a scroll ...that is invisible.

Magicians Hat - When placed on a figure made of snow, it creates a snow golem.

Hasta Pinata - This sword is capable of causing grievous wounds. Every point of damage caused transforms the blood of the wounded into a piece of candy.

Serving Platter - This platter gives advantage to skill checks to carry things upon it and a command word will serve the items upon it or clear a table of items.

Shoes of the Butterfly - Very pretty shoes that allow the wearer to float an inch above a surface as long as they do not move in a straight line.

Quote from Wysperra >>

Are you saying that you want to have a campaign or part of a campaign based around a shop keeper sending the party out to find wierd magic items?

That sounds pretty cool.

Sunglasses at Night - They allow the wearer to see in the dark. It's because when worn the glasses create magical light that dispels darkness.

Candy Canes - They can provide nourishment for a day or you can suck on them to create a dagger that lasts an hour.

Scroll of Invisibility - It's a scroll ...that is invisible.

Magicians Hat - When placed on a figure made of snow, it creates a snow golem.

Hasta Pinata - This sword is capable of causing grievous wounds. Every point of damage caused transforms the blood of the wounded into a piece of candy.

Serving Platter - This platter gives advantage to skill checks to carry things upon it and a command word will serve the items upon it or clear a table of items.

Shoes of the Butterfly - Very pretty shoes that allow the wearer to float an inch above a surface as long as they do not move in a straight line.

 

 Thanks! And yes that is the campaign idea. The shop owner is a capitalist demilich who feeds on magic items instead of souls. He is dying (again) because of a dire magic item shortage in the region.

My campaign has a raccoon artificer named Dave who gives the party deals on magic items in exchange for testing his experimental products. Some of those experiments include:

Dave's Concentration Counteractor

A coin-sized piece of amber with a mosquito inside which hangs from a silver chain. This pendant can be heard to buzz very faintly in quiet environments.

The pendant has 3 charges. As an action, a character attuned to and wearing the pendant can expend a charge to unleash an ethereal cloud of mosquitoes against a creature they choose within 60 feet. This cloud hits the target 3 times, dealing 1 magical piercing damage each time, then dissipates. The target has disadvantage on saving throws to maintain concentration prompted by the cloud's damage.

(Do not show this part to players:

After the final charge is expended, the pendant explodes into a swarm of ethereal mosquitoes. The wearer must make a DC 10 Dexterity Saving Throw or be covered in ethereal mosquito bites for 10 minutes; a creature covered in these bites cannot concentrate on a spell.)

Dave's Randomness Recalibrator

A small charm made of rabbit hair (sustainably sourced from the barber down the street) that can be worn around the wrist or attached to a bag. While attuned to and wearing this charm, a creature's attack rolls are considered Critical Hits on a roll of 19 or 20.

(Secret effect, players keep out:

When a creature attuned to and wearing this charm rolls a 1 for an attack roll, treat that attack as a Critical Hit. Immediately after the attack is resolved, the charm explodes into a cloud of rabbit hair. The wearer must make a DC10 Constitution Save or be unable to take Actions or Bonus Actions until the end of their next turn, as they are overwhelmed by sneezing and coughing.)

Dave's Wellness Ward

(this one is a doozy)

Dave makes things other than protective charms, but after experiencing his amulets my players opted not to test his experimental magic weapons.

Powerful and Silly... hm... these are some of mine:

Mage Gloves of the Facepalm - allow you to cast Hideous Laughter as a reaction if the spell you just cast was totally ineffective.

Boots of Bouncing - When a creature wearing these boots falls from a height of more than 5ft they make a Dexterity saving throw (DC 10) on a success they take no falling damage and instead bounce back up and down halving the bounce height after each bounce, on a failure they take half the normal falling damage and bounce in a random direction in a horizontal arc covering a distance equal to half the original fall height.

Bridle of Resizing - While touching the head of a creature that creature grows or shrinks to be the perfect size to fit into the bridle to be ridden by the user. (does not tame the creature in any way)

Dagger of Honesty - deals 2d4 radiant damage on a hit, but while attune to it you are incapable of lying, and take 2d6 psychic damage and are stunned for 6 seconds if you attempt to lie.

Sticky Green Goo (potion) - One vial of this goo is sufficient to cover a 5ft square area or an object that is no more than 5ft in any dimension, it can be poured on the ground of thrown with a range of 20ft/40ft. The goo remains in a liquid state while within the vial but begins to thicken and become sticky when exposed to air. The goo stays sticky for up to 8 hours or until it is washed away by 50 gallons of water. Any creature that touches the goo, e.g. by entering the area, immediately becomes stuck to it. A stuck creature can use an action to make a DC 15 Strength saving throw to break free of the goo.

Dancing Shoes - While worn they grant advantage on acrobatics checks and performance checks related to physical movement. On command they animate and dance on their own moving up to 30 ft on your turn. When the shoes enter the space of another creature, that creature must succeed on a DC 13 Dexterity saving throw or fall prone, having tripped over the shoes. The shoes stop dancing only if a creature speaks the correct command word.

Frying Pan of Twacking - counts as a +1 club, but on a critical hit the pan makes a loud ringing noise which deals an additional 2d6 thunder damage to the target and the target is deafened for 1 minute.

Stuffed Weasel - When the correct command word is spoken, magic causes the weasel to be partially animated, allowing it to keep watch in all directions and scream to alert creatures within 60ft of it to the presence of unauthorized creatures it sees or any attempt made to move it. However, it cannot move or attack. The weasel revert to an inanimate form after 8 hours or if the correct command word is spoken.

Movable Mansion - This ordinary blue wooden door floats 1 ft above the ground.  When opened, the door grants access to a magical extra-dimensional mansion which acts like magnificent mansion where any creature within the mansion can affect its appearance as if they had cast the spell. If Dispel Magic is cast on the door, it explodes dealing 8d6 fire damage in a 10 ft radius and any creature / objects within the mansion are jettisoned outside the door, the door cannot be opened again until 24 hours have passed. A creature outside the door can lift, push, or pull the door as if it weights 500 lbs, however it always remains vertical with respect to the ground.

Raknor's Happy Fun Hat - This "hat" is the creation of the famous barbarian Raknor. It is made from a steel bucket painted white with a smiley face painted in blood on it. Wearing the hat grants Advantage on all Charisma checks.

Spiked Collar - This black leather collar is studded with 4-inch long steel spikes, you gain resistance to acid damage, and you have advantage on saves to avoid being swallowed.

a table. that allows the attuner to force you to roll on a table you made for campaign prep as if it was a natural roll

a mask that looks like an elf. it makes you look like and orc

a bowling ball that grows exponentially if you roll it

a globe that can teleport you to anywhere your fingers touch on the globe. don't run your fingers over it

a talking skull that tells the future. nonstop.

a dried octopus carcass that can cause a creature's lungs to fill with ink

Beehive On A Stick: a mace that's actually just a beehive on a stick.  On an attack roll of a natural 20, a Swarm of Insects (Wasps) exits the hive and attacks the creature that was last struck by the mace, taking their turn immediately after the wielder's initiative.  The swarm uses the wielder's melee attack bonus, its attacks are considered magical, and it lasts for three rounds once summoned.  A new swarm may not appear so long as there's a swarm currently out.

I recommend you watch "Relics and Rarities" on Youtube for inspiration

There is an official Bag o Beanz. Also you can use animated armor as normal armor or what have you.

A silly arcane item. Star Light-a ring that shines a light as one those glow in the dark things. A powerful arcane item. Monster Tome-has full knowledge of all monsters (except unique ones) in alphabetical order. This tome grants full knowledge of all monsters including their true names. You may use a page of this book to summon a monster who will willingly serve you for life. Once you summon a monster that monster's information is erased from the tome. I am guessing that you cannot scribe any of the pages of this tome.  

THE HE-MAN SWORD! I HAVE THE POWER!!!!!!!!

The Big Red Button. Doesn't do much, but if you press it, everything within a 5 mile radius (excluding life forms) turns into dynamite and explodes. (or some other ridiculous effect of your choice)

Minigun. A really small pistol or musket that shoots foam bullets.

Unmoveable Armor: a suit of plate armor that makes the wearer immune to all forms of forced movement.  Unfortunately, it accomplishes this because it's so heavy that the wearer can't voluntarily move, either: their speed is permanently set to 0 while wearing it and they can't benefit from any increases to movement.

The Absolutely Not Cursed Ring. This ring is cursed, making the wearer believe the ring is absolutely not cursed. However, all other creatures within 10 feet of the wearer can instantly recognize the ring is cursed. However, any persuasion check to convince the wearer of the curse automatically fails. 

- The above ring has no mechanical benefits or detriments. Its just a funny roleplay device to strike up conversation with PC's or NPC's. 

Bracers of Puffy Punchers. While wearing and attuned to these bracers, you can use a bonus action to activate them for 10 minutes. When you do, your fists grow to 4 times their normal size. When enlarged, you have have a +1 to attack and damage rolls with your unarmed strikes. Additionally, your unarmed strikes deal 1d10 plus your Strength modifier. After activating this feature, you have an insatiable hunger for spinach. You must finish a long rest to use this feature again. 

- This is an obvious nod to Popeye and just funny. But it also is a powerful mechanical advantage. 

A powerful sentient sword of [INSERT ENEMY HERE] slaying.

Give it a bunch of mad abilities against the chosen enemy.

The caveat here is that it's cursed and doesn't like to attack anything but the chosen enemy because everything else is "Icky". So it will resist any attempt to use it against other creatures...

"Nuh uhh...nope...you're not going to stick me into that repulsive thing..."

"How DARE you suggest that I should be plunged into that..."

A sapient Carpet of Flying that has severe acrophobia and as such refuses to ever fly more than three inches off the ground.

There are some legendary items from stories that in retrospect are a little silly

• Armor of the green knight- A suit of green full plate that gives you immunity to dismemberment.  For example you can't die from decapitation  by a vorpal sword . However you can still be cut into pieces, if  a move would decapitate you then your head still comes off, you just don't die. . You can also remove your head or limbs as an action and put them back on again as an action. If you take the armor off while in pieces then you lose what ever was cut off as if it had been cut off normally. 
• Argalia's lance - a lance with a golden tip that doesn't do any damage but instead causes those hit to be cursed to trip over on their next turn.
• Gae bolg- A legendary spear with seven heads that when  thrown will pierce every part of an enemies body.  However it needs to be thrown with a secret technique involving throwing it with your feet. Also when used the barb spread through out the enemies body and you need to cut them out to retrieve the spear.   Basically a spear that if you throw it with your foot it does 7d6 damage  but you can't retrieve the spear until you kill the target and no one is proficient with throwing a spear with their feet. 
• Girdle of Brinhilde - Woman's underwear that acts as a belt of giant strength but only if you are a virgin. 
• Shoes of Vidar- Indestructible shoes. Your feet will take no damage while wearing them but if anything hazardous goes above the ankles they offer no protection. 
• Dáinsleif - Damage from this weapon lowers the enemies maximum hit points by an equal amount ( aka damage cannot be healed) . However when drawn, it  cannot be sheathed without killing something.  You literally cannot sheath or drop it, you can give it to some one else but otherwise it is basically stuck to your hand and won't fit in any sheath. 
• Necklace of Harmonia. It make you look eternally  young an beautiful but is cursed to bring bad luck. It makes you look supernaturally attractive but while wearing it the DM can ask you to  roll any checks they choose at disadvantage. I recommend making them into a clumsy  bimbo/ himbo with it.