Rated F
You think of Quentin Tarantino and Kevin Smith right away, when asked which films drop the most f-bombs, but you'd never think anyone actually spent time charting this potty-mouth parlor game on a graph.
Wikipedia has what you're looking for. A list of the films that use the word the most, including a f-per-minute rate.
You think you know the winner?
Smith scores particularly high, Jay & Silent Bob Strike Back coming in at No. 15, Chasing Amy tied for 39th and Dogma at 40. Tarantino is a deacon compared to that, with only two raters: Pulp Fiction scoring number 11 and Jackie Brown at 33.
The winning 1997 flick uses the term 470 times in its 128 minutes. If you censored the film, the script would be 5 pages. (I made that up.) But that's almost once every 15 seconds.
Gary Oldman's Nil by Mouth, a British film set in working-class London, gets the prize. IMDB's trivia page shows that the movie was semi-autobiographical.
Oldman dedicated it "to my father." That #$%^*
Remember Steve Martin's dropping the f-bomb every other word when berating Edie McClurg at the car-rental counter in Planes, Trains, and Automobiles?