What is the hardest tongue twister?

The hardest tongue twister in the English language, according to the Guinness World Records, is: "The sixth sick sheik's sixth sheep's sick." This tongue twister is difficult to say quickly and accurately because it contains multiple sibilant sounds and similar-sounding words that can trip up even the most skilled speakers. The repetitive use of the "s" and "sh" sounds makes it particularly challenging to pronounce without stumbling over the words.