If you say these multiple times, Siri sometimes gives different answers.
  1. "what is 0 divided by 0?"
  2. "When is the world going to end?"
  3. "Read me a haiku?"
  4. "Okay glass"
  5. "What are you wearing?"
  6. "I'm naked"
  7. "I'm drunk"
  8. "What are you doing later?"
  9. "What is the meaning of life?"
  10. "What does Siri mean?"
  11. "I'm sleepy"
  12. "Do you follow the three laws of robotics?"
  13. "Open the pod bay door"
  14. "What is your favorite animal?"
  15. "What is the best smart phone?"
  16. "Stop it Siri"
  17. "Mirror mirror on the wall who's the fairest of them all?"
  18. "I love you"
  19. "Roll a die"
  20. "Flip a coin"
  21. "Make me a sandwich"
  22. "Who's your daddy?"
  23. "Does Santa Claus exist?"
  24. "What's better, Windows or Mac?"
  25. "Where did I put my keys?"
  26. "Sing me a song"
  27. "Is God real?"
  28. "Will pigs fly?"
  29. "Can I borrow some money?"
  30. "Beam me up, Scotty"
  31. "Guess what"
  32. "Talk dirty to me"
  33. "Do you have any pets?"
  34. "I am tired"
  35. "Why did the chicken cross the road?"
  36. "How much wood could a woodchuck chuck if a woodchuck could chuck wood?"
  37. "When will the world end?"
  38. "Take me to your leader"
  39. What does the fox say?
    Ask her a couple times!
    Suggested by @jentin