What is the worst tongue twister?

Peter Piper picked a peck of pickled peppers
As far as the Guinness Book of World Records, this is the worst: "The sixth sick sheik's sixth sheep's sick." However, the Massachusetts Institute of Technology think there is a new contender for that spot. They feel that "Pad kid poured curd pulled cold" is the toughest there has ever been. As for me, I can't say either one of them, so it's kind of a moot point on this end.
For me, the worst tongue twister is the Sally one.