Message Blast (CR 6)
As you walk into the room, you begin to hear whispers, which get louder.
Type: magical; Perception DC 25; Disable Device 25
Trigger location; Reset None
When a character sets off this trap, he begins hearing voices as per the message spell at CL 6. The messages build up to a dull roar, and last for an hour unless dispelled. While hearing the message, a caster must make Concentration checks in order to cast spells, and all skill checks are at -2.
What makes this trap work is that it is pretty harmless by itself. However, if you place this in a situation in which casting or skill checks are going to be needed, it becomes quite effective. As an added plus, many cantrips, this one included bypass Spell Resistance and have no Saving Throws, so even the most twinked out party is not immune. You can also use something like this to push a storyline. Perhaps the incessant whispering stops if you answer riddles correctly, or maybe this is a side effect of a haunt. In any case, whatever you choose, you should have fun, especially if you ham it up and act out the whispering.