Show: Pretty Little Liars (ABC Family)
Pretty Little Liars isn't usually included in any conversation about great television, but the show knows how to drive fan excitement in a way that many headier shows wish they could harness. Mona (Janel Parrish) being outed as "A" was a shock to the system of teens and tweens everywhere who had been long awaiting the revelation. The creative team turned the event into more than a spoiler, however: They used the revelation to drive fan interest beyond the events of season two.
Like most long-running shows these days, Pretty Little Liars is based on a series of books. Any of you Game of Thrones fans out there know that books and their snooty readers often act as the ultimate spoilers. The team behind the Pretty Little Liars TV show has created enough distance from the books that fans that have read them can't be sure that they have a clear road map of the series. After Mona was outed as A, she was visited by a mysterious figure, which was perhaps a nod to the book's reality that there is more than one A. Essentially, the staff used the books as a way of turning what would have been a definitive spoiler into a question to generate discussion and build excitement for future seasons. Rather than ruining viewing for those who hadn't watched the show yet, spoilers served to further excite the fan base.
This is such a savvy move that we wonder if Benioff and Weiss might take a page out of Pretty Little Liars playbook as they run out of canonical story and catch up to Martin's books on Game of Thrones.