Paranoid Delusions (CR 8)
The air is thick with moisture.
Type: magical; Perception DC 33; Disable Device 33
Trigger location; Reset None
When the trap is triggered, the PC feels vaguely unsettled. The next time they use an item together with a roll, like a skill check or attack roll, they must make a DC 25 Will Save. On a failure, they become unable to use that item for the next 1d6+2 rounds, believing that the item is cursed and will betray them. On a success, the PC takes a -2 circumstance penalty on the next single action with the item.
This trap works well at the beginning of an encounter area that requires combat or skill checks. To play this up, have the item in question trigger vivid hallucinations, or even have it mildly injure the PC. A sword could seemingly cut the wielder or an item could suddenly appear cursed or evil. With good enough descriptions, even non-affected PCs may think twice about their own inventory when sizing up an encounter. After all, there are plenty of other reasons they could feel uneasy.