In
James Cameron's 1984 movie
The Terminator,
Arnold Schwarzenegger (who plays the Terminator) visits the police station where Sarah Conner (played by
Linda Hamilton) is being interrogated and guarded. He asks for Sarah, but the clerk tells him it will be a while before she'll be done, and tells him he can wait on the couch.
Arnie then speaks the immortal words
I'll be back., which will become his
trademark, along with his muscles, his stupid accent and, later on, his crappy movies.
In most of the movies he made in the years after The Terminator, he says those immortal words. By the time he made 1993's Last Action Hero, he was aware it became silly to say it in every movie, so they decided to make fun of it too. In this movie, he plays a character in a movie. When a kid accidentally is transported from the real world into the movie world, and Arnie tells the kid he'll be back, the kid replies "I knew you were gonna say that. You say that in all your movies."
I must admit I haven't seen any of his movies that came out since Last Action Hero, so I don't know if he lets everybody know he'll be back in them, but I know he says it in the following movies:
He probably says it in the other movies he made between The Terminator and Last Action Hero too, but I couldn't remember it, so please /msg me if you know a title that isn't in the list.