When "Beam me up, Scotty!" will not suffice and good 'ol gravitational assist will. List them here!
  1. Star Trek IV: The Voyage Home (1986)
    Kirk, Spock and co. slingshot around the Sun to travel back in time and kidnap humpback whales that will decide the fate of future Earth.
  2. The Martian (2015)
    Crew that left Matt Damon behind on Mars feel guilty and slingshot around Earth to go back and rescue him.
  3. Appolo 13, it's just a moon instead of a planet
    Suggested by @beanybeans