I'm thinking about creating a world where anything with magical powers are known to make their wielder both blessed and cursed in some way, some more severe than others, sometimes in equal measure. The world is also low-magic.
If the cursed item is always giving a disadvantage, players will just sell the item, but if it's designed well they can use it to their advantage.
An example could be an armor piece which gives you immunity to fire, but you receive double cold damage.
I would add a rule that you can't have two of each in effect and they disable eachother, otherwise you could be immune to every type of damage for example. We wouldn't want that, right?
I've found a question with an answer that I really liked, where the party has received a +4 sword, but the wielder goes into a frenzy mode and attacks on sight until everyone has died, including allies. Maybe not all items are this way, but more like legendary items or something.
How do I create magical weapons with side-effects in a low-magic world in a way that players still want to use said items?
Best Answer
In a campaign with few magic items, any magic item will be valuable
If the GM explains beforehand that the campaign will have very few magic items, and it's level 6 before the PCs get their first +1 longsword, the PCs won't care that while the +1 longsword is wielded, the wielder's hair turns blue or his fingernails get all pointy, but they will care if every time the sword's swung someone the wielder loves bursts into flames and dies.
In other words, a curse must be appropriate for the item's power.
Fortunately, Pathfinder already breaks down magic items into six broad power categories—lesser and greater minor, medium, and major items (e.g. magic armor, wondrous items)—, and Pathfinder provides a list of common curses found on items, the Drawbacks table probably being the most useful. You'll have to develop house rules from there depending on how cursed you want items to be, but that's a reasonable place to look for inspiration. (I suspect most PCs would be wary but still use magic items if the magic items had 1 drawback if minor items, 2 if medium, and 3 if major and adding an additional drawback if greater, but I can imagine a campaign wherein magic items were hated and feared if these numbers were, for example, doubled.)
An alternative: Blood Artisan as the default
That is, make cursed items common but also cheaper. The Dungeons and Dragons 3.5 ancestor feat Blood Artisan has the following as its benefit:
Having this feat's effect be the default effect for all item creation feats and there being no way (or only a secret way or a way that's onerous like taking another feat such as, hypothetically, the feat Improved Craft Wondrous Item) to make uncursed items makes for a campaign in which magic items are cheaper and still readily available but usually cursed. Then PCs must shop around for items having the least bad curses, which, while it might be initially interesting, is liable to become dull in the long run.