
Charon Onozuka |

I’m currently designing a black market for my players to encounter in my campaign (evil campaign, players will have a bit of trouble shopping at normal stores after what happens). The idea is that a malicious NPC with levels in Hoaxer Bard has purposely created several cursed items and mixed them in with all the deals and scams already taking place in the black market.
So my question is, what are some good/fun cursed items to tempt my players with when they see them for sale?

Wonderstell |

Sell them "continuous" items with a set amount of charges. Even as they examine or use the item they'll get the effect they want... for a limited amount of time.
Other more annoying curses would be:
You'll always find hair in your food.
You bleat like a sheep when you climax.
You always end all your lies with "...NOT!"
Everytime you speak, people feel compelled to talk over you.
Do you want to trick your players into buying cursed items which aren't what they want? Or do you want them to buy working items with cursed secondary abilities, which would tempt them to use the cursed items, even if they suffer the curse?

LordBiBo |
Actually, 2nd edition dungeons and dragons had some of the best cursed items out there. They did all sorts of weird things and most of them have been lost to time though some have filtered into more modern versions of the game (including pathfinder). My friends have made up some fun ones too. I tend to prefer cursed items that are useful but have some drawback as opposed to things that just get the pcs killed.
Some of my favorites included:
Ring of Contrariness - It works as a normal magical ring (whatever you like, though there is a list to roll from) but the character is unable to agree with any idea, statement, or action while it is on.
Wand of lightening - unlike the wand of lightning that deals horrible death to all before you, the wand of lightening just makes things 50% lighter (admittedly not a curse per se, but amusing none the less)
Ring of Bureaucratic Wizardry - functions just like a ring of wizardry but every time the wizard attempts to cast a spell, a sheaf of papers and a quill pen suddenly appear in his hand. The papers are forms that must be filled out in triplicate explaining the effects of the spell, why the wizard wishes to cast it, whether it is for business or pleasure, etc etc etc. The forms must be filled out before the effects of the spell will occur. The higher the level of the spell cast, the more complicated the forms become requiring one round per level of spell.
Ring of fire resistance that only functions underwater
Ring of water breathing that prevents the user from breathing air until remove curse is cast

DM_Blake |

Why did this bard do this?
Creating a cursed item is exactly as expensive as creating a good item, but it is useless to the creator (at least, useless int he context of what he was trying to make).
Is this bard just super-meaga-wealthy with nothing but time on his hands? And a giant d-bag besides?
Would a more sensible story be that someone came into possession of some cursed items accidentally* and sought to off-load them on the seedier elements of society by selling them in the black market?
*Two methods come to mind: 1) a group of crafters (e.g. a Golarion magical sweat shop) who are paid to crank out magic items by the scores have, over a few years, created a handful of accidents that were thrown into storage until just now when an enterprising middle-manager decided to get some extra profit or 2) a large retailer who buys and sells magical items has, occasionally, been fooled by a cursed item and ended up buying a few over the years that he couldn't resell, but he just thought of a solution to profit from these on the black market.
At least to me, those sound more likely than some jerk bard spending a few months of his life and tens of thousands of gold pieces just to prank some black market shoppers.
In any case, the items you want to use are fake versions of stuff your PCs really want. I have a PC in my game right now with a sword he thinks is +2 but it's really -2. He loves his sword but hasn't yet figured out that it's hurting his attack chances (it's relatively new to him). Another good choice is the Bag of Devouring (where's Gorbacz???) - everybody likes bags of holding, probably some PC will go shopping for one (you can make sure they do by giving them an encounter that has a literal ton of loot - don't give them 1,000gp; give them 100,000 CP instead and then ask them how they'll transport it).

Charon Onozuka |

Why did this bard do this?
Div with bard levels.
Basically, the Div is trying to screw with mortals for kicks and to enjoy their suffering. To that end, they have their hands in the drug trade (get mortals hooked on things that ruin their lives, yet they still want more) and the black market (easy to unload cursed items, then watch as people fight over them & ultimately ruin themselves when trying to use said items).

Wonderstell |

@DM_Blake
Creating a cursed item is exactly as expensive as creating a good item, but it is useless to the creator (at least, useless int he context of what he was trying to make).
Actually, deliberately making an item cursed does more often than not reduce the cost of said item.
For example:
Creating a cursed Belt of Giant Strength which tricks its user into believing it works, when in reality it doesn't, would be made with only a tenth of the original cost.

LordBiBo |
I gave this one to the leader of a thieves' guild once. He lost it when his ring of invisibility suddenly fell into the hands of the PC rogue...
Sword of Suspicion
This appears to function as a +2 longsword in all respects until it has been used by the wielder to slay a living creature. Afterwards it functions as a -2 longsword, though the wielder is convinced that it still functions normally. It also provides the wielder with haste as cast by a 5th level caster once per day and glows red whenever an item is stolen from the user.
However, a week after the weapon has been activated, the user begins to find things missing. There is a 50% chance per day that one of the user's belongings is teleported into a nearby ally's possession. Typically such items are small, but valuable such as coins, gems and rings (the GM chooses the most valuable yet suitable item). Once it does this, the sword glows red to alert the user that something has been stolen.
Should the user choose to draw the blade against an ally, it always provides a +5 bonus and causes the user to single-mindedly attack that ally (using the haste ability if available) until the ally is dead or a remove curse spell has been cast, which allows the user to sheath or discard the sword.