Terminator 2
The Daddy, in every sense. It's the best action film in the pure sense of capturing the kinetic feeling of action, but it's also a step above its peers in telling a meaningful story and telling it well. It's not a masterpiece or anything, but it is the best action film ever made.
The Matrix
For a certainly generation, Star Wars was 'their' film, for another, Indiana Jones, for my generation, I feel like The Matrix was that film. I say that, to indicate I may not be really objective about this film, it has a lot of nostalgic weight to me. It is so so good though.
Die Hard
The best protagonist in any action film, and the best antagonist. Should have been left well alone, the sequels are all terrible.