Commando, because I started lifting after seeing Arnie in it for the first time.
The Fountainhead - maybe not the movie so much, but the book definitely, for the concepts in it and characterization of Howard Roark & Gail Wynand.
And any movie where the underdog wins in the end after getting beat down by life hard - like Hidalgo and Cinderalla Man. Not life changing, but inspiring / gives you hope.