The movie Machete was made after the trailer. The trailer was sandwiched, with other fake ones, in between the two parts of the Tarantino / Rodriguez double-feature Grindhouse. I remember because I saw Grindhouse in theaters and years later saw the actual trailer for the real movie Machete and did quite the double take. What a B-movie clusterfuck.
Last year Eli Roth did the same thing with his Grindhouse trailer, turned it into a real movie.