For those who need to shake up their novel a bit, here is a list of plot twists to consider. If you don't need a plot twist, consider leaving one of your own in this thread. :-)
Hero returns in triumph only to find... tragedy!
It comes to life...
It comes to life again!
But he escaped!
But he hid how badly he was hurt...
Hero makes a bad decision but it proves to have hidden benefits.
Hero's mentor was secretly working for the Adversary.
Hero is scarred by encounter with Adversary.
Adversary gets to the clue holder before Hero.
Hero is constrained not to reveal true identity and therefore loses face with his/her true love/family.
Hero's good friend has a nervous breakdown at a critical juncture.
Adversary kills Hero's mentor
Adversary makes Hero choose between a large group and his/her beloved.
Hero is dismayed by new truth
Hero encounters a perfect double.
Hero creates a _______ machine.
Hero discovers that he/she has been spied upon.
Levees break in the storm.
Hero discovers lost city.
The Adversary rigs the election.
Adversary discovers plot by Hero and kills one of the Hero's friends.
Hero's intended misguidedly marries Adversary.
Hero's allies despair of all hope, ending in tragedy.
Hero must choose between mentor and true love.
It was all just a dream.
Character dies.
Someone gets kidnapped.
Someone fakes their own death.
Surprise visit from former lover.
Character has an accident and slips into a coma.
Character is betrayed by a friend.
Hero gets amnesia.
It wasn't an accident.
There is a new addition to the family.
Hero is publicly embarrassed/shamed
Someone is sued, but it is a case of mistaken identity.
Someone's identity is stolen.
A close friend dies.
A character is diagnosed with a terrible disease.
A character develops strange powers but can't tell others about it.
The Hero's goal would adversely impact sympathetic allies.
A ghost appears with dire warnings.
Villain's beautiful daughter falls in love with Hero (or vice versa).
Hero is struck blind.
Cubs win world series.
True villain was Hero's father.
Critical machine is sabotaged.
Hero's best friend is in jeopardy and only the Adversary can save him.
A secret identity is revealed.
Hero and Adversary are stranded together and must work together to survive.
Hero is framed by Adversary
Hero falls in love with Adversary
Hero is maimed, disfigured.
Friends and/or lover believe that Hero acted out of cowardice
Hero is exposed to the bigger picture
Unforeseen disaster threatens all
Hero requires the Adversarys help to save the city/village/his friends
The Adversary needs the Heros help against a new threat
She is dying of an incurable disease but hides this from everyone
Hero is fired
Hero has a mental breakdown
Hero is faced with a challenge that is reminiscent of one he/she failed before
Hero experiences a Vision
Adversary decides to become a Hero but no one will trust him/her
For those who need to shake up their novel a bit, here is a list of plot twists to consider. If you don't need a plot twist, consider leaving one of your own in this thread. :-)