This one doesn’t really apply to me as I’ve never walked out from a movie in my life. Ticket prices are nasty enough for me to not sit a movie through to the end when I’ve paid for it. Besides, you never know. Maybe the film picks up later on.
But while I may not have left a theater, there are a few movies that have managed to put me to sleep, which seems a close enough substitute. Chief among these would be Driven, a largely forgotten 2001 racecar movie starring Sylvester Stallone, Kip Pardue and Burt Reynolds. Such a dull film, but a great incentive to go on vacation to dreamland. Then all of a sudden a high-speed car ride through a big city woke me up, before I realized that the film was still really boring, so back to sleep I went. Me and the friend I went with were both terribly disappointed, and we actually made a vow to one day go see a good Sly film in theater to make up for this travesty. It took nine years until The Expendables made this happen.