Monkey's Paw kind of toys

[qazy123]

So, my players are hammering me for more magic thingies... They have earned some of the magic stuff they have but they are being greedy so I want to teach them all their lesson by giving them really rigged magic stuff
Things I have:
Never miss: It never misses... Even if it hit's an ally
Soul sucker: It grows stronger when it kills things but will try to steal the users soul.

[Fuzzy-Wuzzy]

You should be able to get some inspiration (or just take things) from Archives of Nethys' cursed items list. Some are paw-like, some are more straightforward.

I hope you have some in-game reason in mind why they suddenly acquire a whole bunch of cursed stuff. A merchant with shockingly low prices, maybe?

[Guardianlord]

Paizo has a GM tool for creating cursed items with a lot of flavorful triggers, conditions, releases, and curses.
Cursed items D20

I hope you have a good reason in game for them finding these items. Evil merchant is a good one Fuzzy-Wuzzy, or a dying foe curses his treasure horde before the final blow is struck, or maybe some long lost treasure chest, buried and forgotten.

[Daw]

You know, you don't have to go the classic route.

Items can be renowned, and draw the attentions of people who might be able to get more out of the item than the players can. Now these people may be reasonable, or vindictive about people sullying their.....

On a related note, items can be very Present, and noticeable by the magically aware.
A party with several of these may never again find an unprepared foe. Now the sale price for such blatant weapons is going to be rather low.

[Reksew_Trebla]

If you wanted to be really mean, give them an actual useful item that is a secret cursed artifact. What it does to benefit the players is up to you, but have it where the cursed part makes it so that all enemies they find magically have powerful gear, that it and all their magic gear they normally had withers away when they die or cease being the PC's enemy, and eventually throw in some confused enemies who don't know how they got their new gear (because you know), suggesting that there is a god or something that just hates the players. Eventually they figure out, from you giving hints in the game, that the artifact they have is responsible for this.

When they go to get rid of it, have it immediately pop back into the possession of one of the players, like how a Monkey's Paw would, except instantly instead of a delay. Then have them research this artifact at the local library to learn the only way to lose ownership of it is to perform a 24 hour ritual where you destroy 10,000 GP (arbitrary value) of prized magic items and then the artifact teleports off of them into another plane.

The only way to destroy it is for two parties of characters to both possess one (as when creating one two are created) and for both parties to start as enemies and then cease being enemies, causing mutual destruction of all of their magic items, including the cursed artifact.

[Fooma]

A wand that is secretly a Rod of Wonder always fun to give out. Have it only worth 1 copper resale (no one is crazy enough to have one laying around in their shop!). After they figure out what it is, the party will be inclined to use it when fun, in a pinch, or when nothing else works.

Be careful though, one result is that it can spit out 10-40 gems that value 1 gp each. Being that the world revolves in gold instead of "gp" this is open to your interpretation. I prefer they can be exchange 1:1 for Gummy Penguins, Goblin Porridge, Granite Pebbles, or whatever the current market can bear. (Intent is to have the rod be something that can be exciting and fun to use, and not a source of income for the party).

[Dastis]

Grimstooth Traps books all had some absolutely lovely trap items

Kobolds of Galorian had a few trapped items

Had 1 sword that made it such that it was the only weapon you could draw and you always had to draw it during the first round of combat. Attached itself like that to whoever first picked it up. Uses up open hands and action economy

Sword of Life and Death. On hit 50% chance to deal positive energy damage(healing) and 50% chance to deal negative energy damage.

Robe of Sticky Items. As Robe of Useful Items but any item you draw has a percent chance to be coated in Sovereign Glue that dries directly after you draw it

Monster Spellbook. A quasi intelligent spellbook that eats other spellbooks whenever it is not being watched. Spells from eaten spellbooks are automatically added to the Monster Spellbook. However difficulty lies in preparing the spells you want. When preparing spells, for any given spell there is a 20% chance that you will not find it in the Monster Spellbook that morning.

[Weirdo]

Unfriendly intelligent items can be fun.

Had a sword called "Purity" in the campaign once whose special purpose was to destroy human crossbreeds - including 3/4 party members (aasimar, tiefling, and half-elf). Fortunately it didn't have a high enough Ego to force anyone to murder their teammates...