Couldn't possibly pick just one. I'll try and limit this to under a hundredish
.
Lost in Translation, Broken Flowers, Untergang Der (Downfall), Eternal Sunshine of the Spotless Mind, High Noon, Toy Story, Cool Hand Luke, American Beauty, Almost Famous.
Now for the obligatories (cue the groans); Forrest Gump, Donnie Darko, Pulp Fiction, Reservoir Dogs, Trainspotting, Goodfellas, The Shawshank Redemption, The Godfather (i & ii).