A place where a fertility spell has gone wrong.Kisses can lead to pregnancy, any fungus infection runs rampant, corn grows as soon as it is planted,ect.
A place where for those who sleep in it,the real life and dream world is blurred-so nightmares can be deadly.
The PC's end up in a strange world where the very rocks are made of gold and jewels.As such gold and jewels is worth very little, but the iron in their swords and belt buckles is suddenly worth a LOT.
A cave full of what appears to be gold nuggets-the nuggets are in fact radioactive and will poison whoever takes them.
A place where scratching an itch is seen as highly rude.The problem is, it's full of biting insects.
There is a place where there are living dinosaurs but in miniture.So there are foot long Tyranosaurus Rex's and four foot long Brontosauruses, for example.
A PC Conjurer or summoner, basically any mage whose sole purpose in life is summoning creatures to aid in battles and various situations, is cursed with a hex, and needs to find a way to undo the curse...before he goes mad, or his fellow PCs throw him out of the party, or worse.
Everything he/she summons, never goes away. So you'll have to figure out what the heck to do with that dire bear or fire elemental once it's done fighting the orcs for you. Eventually a caravan of bizarre creatures either annoyingly ends up following the summoner around, or they go off to cause mayhem elsewhere. Bad news for the poor spell-caster regardless.