1. "An Inconvenient Truth" (2006)
For years ecological concerns were considered strictly for the Birkenstock set, until the cause found its rock star in Al Gore. With his PowerPoint presentations about climate change, which formed the heart of Davis Guggenheim's double-Oscar-winning documentary, the former Vice President made the information understandable and scarily relatable, even funny at times. Without the platform the film provided, you really have to wonder how long it would've taken legislators to start talking seriously about the subject and whether we'd be as inundated today with "green" marketing campaigns, reusable shopping bags and compact fluorescent bulbs.