6. Firefly, "Bushwhacked" (Season 1, Episode 3)
Ah, the short-lived, oft-lamented space western created by that guy who would go on to write and direct The Avengers....Joss Something-Or-Other. For most people, the show's reputation precedes it: cancelled by Fox after only fourteen episodes were produced, it gained an incredible cult following on DVD, leading to the sequel film Serenity, a handful of one-shot comic spinoffs, and the recently-announced comics continuation from Dark Horse. Bushwhacked is the perfect introduction to the series because it is not only a great story, but one that touches upon every aspect of the Firefly 'verse. Every member of Serenity's crew gets their moment(s) to shine in the episode, but those moments are more than just 'shiny'- they give us a look straight to the core of each person. The episode takes us beyond the hull of Serenity and introduces us to the wider universe and the groups that inhabit it from the vicious, unseen Reavers to the crisp, sterile Alliance and shows us how they all fit together. If you're not aiming to misbehave after watching, something's wrong.
Honorable Mentions: Serenity, Out Of Gas