Non-examples:

• The cursed pieces of eight from the first Pirates Of The Caribbean movie; the nine pieces of eight in the third movie might count too.
  • It doesn't count because the whole point of the nine pieces was not to collect them but to let everyone have only one.

Hence, it's not an example.

• The Ghostbusters have to collect all ghosts in New York.

How is it an example? Okay, Ghostbusters catch ghosts; gathering ALL the ghosts isn't a part of the film plot at all (and would be an exercise in futility). Perhaps it was referring to some video game adaptation?

• Three Gotta Catch Them All with a twist that made them Gotta Kill Them All:
  • Battle Royale counts as a kill all characters.
  • In Gremlins, if you didn't collect(=kill) all gremlins, the survivor(s) would make more of themselves.
  • Kill Bill is this.

Hence, it doesn't belong here, but to Gotta Kill Them All.

• In The Fifth Element you had to get all elements together to save the universe.
  • But you get the first four as a box set, and the fifth falls into your taxi at the beginning of the movie.

Hence, the box of elements is a Mac Guffin, and the Leeloo is a Mac Guffin Girl. Not an example.

• Thinking about it again, Leeloo doesn't really fit the description of Mac Guffin Girl - is there some other trope that's a better match?