The DVD box (spoilers)!
AH, just finished watching this and guessed the twist just as the cars crashed. I probably wouldn't have guessed it, if it wasn't for the DVD box which on the back says 'In the tradition of 'The Sixth Sense' and The Others' So I instantly thought it would be a twist where the main characters would be dead and not know it.
So annoying that's there!
Get it, Got it, Good!