What are most difficult tongue twister?

It's hard to definitively say which tongue twister is the *most* difficult, as what's challenging depends on the individual speaker. However, here are some notorious tongue twisters known for their complexity:

Classic and Difficult:

* She sells seashells by the seashore. The shells she sells are seashells, I'm sure. So if she sells seashells on the seashore, then I'm sure she sells seashore shells. (Lots of sibilant "s" sounds, tricky repetition)

* Peter Piper picked a peck of pickled peppers. A peck of pickled peppers Peter Piper picked. If Peter Piper picked a peck of pickled peppers, where's the peck of pickled peppers Peter Piper picked? (Repetition of "p" and "ick" sounds, long sentence structure)

* Betty Botter bought some butter, but the butter Betty Botter bought was bitter. So Betty Botter bought some better butter to make the bitter butter better. (Similar sounds and repetition, tricky "b" and "t" combinations)

* How much wood would a woodchuck chuck if a woodchuck could chuck wood? (Difficult "w" and "ch" sounds, awkward phrasing)

More Challenging:

* The sixth sick sheik's sixth sheep's sick. (Difficult "s" and "sh" sounds, tricky consonant clusters)

* Two tiny tigers take two taxis to town. (Difficult "t" and "x" sounds, alliteration)

* Unique New York, unique New York. (Difficult "y" and "k" sounds, tricky rhythm)

* Fuzzy Wuzzy was a bear. Fuzzy Wuzzy had no hair. Fuzzy Wuzzy wasn't fuzzy, was he? (Repetition of "f" and "z" sounds, difficult rhythm)

Ultimately, the best way to find the most difficult tongue twister for you is to try them out! You might discover a new one that gives you trouble.