Star Trek II - The Wrath of Khan
Among the very best of the old school Star Trek films, Wrath of Khan features a great sacrifice from one of the series' most beloved characters. (HUGE SPOILER AHEAD!!!!) The character is, of course, Spock, who, in a move no Trekkie at the time could foresee, bravely risks his own life for the Enterprise and dies in the process. This sets up the basis for the 3rd Trek film, the under-rated Search For Spock, which had its fair share of tender moments as well.