15) Dead magic area with a tribe of orcs/ogres/trolls
16) The appearance of a walkway across a river of lava, a huge reward is at the other end, can't fly over it, have to walk over it. But to walk over it, they must have the bloodline of the person who created the bridge or suffer 10d6 points of damage each round, no save. It takes 5 rounds to cross the whole length of the bridge.
17) Inherit/found/given a sword, during combat the sword deals maximum normal damage at all times, but it also inflicts the same amount of damage on the cleric, when cleric perishes, it moves to the next spell caster, then the highest hit point character until it starts to hurt the weilder.
18) Inherit/found/given a sword that is a +3 keen weapon, unbeknownst to the players, the sword is cursed, all opponents of the weilder gain an SR 20 and regen 5 when the sword is used against them.
19) Find a scroll revealing the location of a sphere of annihilation, when they get there the sphere has grown a semi sentience and is going after all spell casters cause they taste yummy to it because of all the spells they memorize.
20) The PC's unearth a cavern , upon exploration they find several Collossal beetles/scorpions/etc. (insert devastation vermin here, of the same type)