Admittedly I skimmed the previous 140+ comments pretty quickly, but am astonished to not see any mention of :
"Stop, or my mom will shoot"
...which is about about as bad as it gets - intending to be comedy but failing entirely.
Fortunately we are graced with some movies which are so bad as to cross the threshold into utter brilliance. I give you:
Bad Taste (http://www.imdb.com/title/tt0092610/?ref_=nv_sr_1) ...Peter Jackson's first commercial movie.
I Bought a Vampire Motorcycle http://www.imdb.com/title/tt0097550/?ref_=fn_al_tt_1 ...Starring Neil Morrissey