Pink Flamingos (1972)
Directed by John Waters
Film Nationality - USA
Poster Nationality - USA
Clearly the least polished poster on the countdown goes to this one for John Waters' ultimate gross-out flick Pink Flamingos. You might not think it to be anything special, but I think it's incredibly crude design holds much more charm than 100 posters for Hollywood movies.
And, hey, if you want your movie to stand out, you could do much worse than sticking Divine on your poster wearing that red outfit and aiming a gun.