Forget simple or subtle
or something so bland you can show up late and not miss anything.
In film, a great opening grabs you by the collar and dives into the story.
In a few quick strokes,the character(s), the dilemma and the boundaries are established or in some cases, just the tone of everything to come. There are so many compelling examples, but I narrowed my list to opening scenes that are primarily without dialogue.
A lot can happen in just a few minutes.
Touch of Evil
West Side Story
The Good, the Bad and the Ugly
Once Upon a Time in the West
The Philadelphia Story
2001: A Space Odyssey