I should have clarified. Movies in which things happen for absolutely no logical reason, except that the writers/screenwriters/director(s) are amateurish and don't think before they do. Examples in the spoilers below. THEY MAY CONTAIN ACTUAL SPOILERS FOR SOME MOVIES, BE ADVISED:
Examples include wrecked cars exploding for no reason, the good guy getting shot in the body 6 times and surviving, while every single one of his shots kills instantly, that fucking idiotic scene in Iron Man 3 where Tony Stark's Mark 42 armor(worth billions) could not get itself out out of a wooden shack before the kid opened a door held closed by a steel chain, the idea in the film that the armor could lose power while the guy had a reactor in his chest generating more energy than a nuclear power plant, the ending of Law Abiding Citizen and Dexter(the TV series) ... just movies with very poorly though-out sequences, gigantic plot holes(doesn't make a difference whether a movie is supposed to be in this reality or another one, every setting has rules, you can't just magically remake them in order to tie loose ends in your stupid story), movies that aren't true to the source material and therefore insultingly bad(Max Payne, looking at you). Movies with scenes like that Die Hard 5 one, where the villains put a device in Chernobyl and it magically disables the radiation in 10 minutes, while John McClane walked around the most irradiated area and didn't die within hours.
Things like these are what makes me consider a movie dumb. Some of these movies are enjoyable, some of these are pathetic. So my question is, what is your favorite dumb movie - a movie which you know has so many errors and inconsistencies, yet you really like it?