Student or Learner
"What's your favorite Saw movie?"
Is it correct to use "what" even though there are seven Saw movies and the answer possibilites are thus limited? I was taught that in such a case one should use "which," but "what" sounds better.
What you were taught is what I was taught at school. I suppose that technically what is not correct, though the 'rule' seems to be observed less and less nowadays, particularly when 'what' is followed by BE, as in your example.
If you rephrased it as, "Wh.. Saw movie do you like best?" I think you would be more likely to hear which.