The NOVA episode devoted to the work of James "The Amazing" Randi makes a nice coda to any science course.
In the end, skepticism and critical thinking are important elements we hope we instilled during the year and will remain with our students long after the formula for kinetic energy has faded.
The full video is on YouTube here:
NOVA: James Randi's Secrets of the Psychics
An accompanying question sheet to help keep everyone engaged can be found here:
Video Questions for James Randi's Secrets of the Psychics.
More skepticism in the classroom lessons and links can be accessed from my Skepticism in the Classroom page.