Writing about set text that wasn't taught in an exam

Out of curiosity, has anyone, either accidentally or on purpose, written about the set text that wasn't taught. Eg, Selecting Hamlet to write about in the exam instead of Macbeth? What was the impact on the grade? I'm slightly tempted to do this with one of the films we are studying and self teach a different one instead.

It would require a lot of self studying and it would mean that you wouldn't be able to collate your notes with your friends from class. However, if you feel more confident with another text then do it. I can recommend a few websites that have decent notes.

1) Seneca learning
2) Quizlet will have some good quotes
3) Physics and Maths tutor
4) Spark notes for quick summaries
5) Stacey Reay on youtube, her videos are so good and she has some really amazing analysis