JFK (1991)

  This movie will have you reaching for your tin foil hats.  I'm not a conspiracy theorist in general and definitely not one about JFK, since I wasn't alive until nearly twenty years after the man's death, but even I started to question the status quo after watching this.  To me, that makes it a stellar movie.

Louisiana District Attorney Jim Garrison (Kevin Costner) begins independently investigating the Kennedy assassination in 1966, after reading the Warren Commission's report and finding some questionable practices.  The more he and his team pick at the threads surrounding Lee Harvey Oswald (Gary Oldman) and his connections to an anti-Castro guerrilla (Joe Pesci), an influential trade commissioner (Tommy Lee Jones) and a former member of the Office of Naval Intelligence (Ed Asner), the more threads there seems to be, evolving into a tapestry of conspiracy stretching from the Pentagon to Dallas and all the way to Vietnam. 

Whether or not you believe in the "Lone Gunman" or the "Grassy Knoll" theories, or don't care at all, this film lays it all out in excruciating detail.  Block out an afternoon, though, because the Special Edition (which I watched) is three and a half hours long.  Plus, you're going to want to follow it up with something light-hearted.