What is the hardest, most difficult tongue twister in English?

I gotta dig bick.

Can 你 can a can as a canner can can a can?

Red leather, yellow leather, red.

Say it three times fast.

Pad kid poured curd pulled cold.

say it 5 times fast .

Sally sells sea shells down 由 the sea shore.

Irish Wristwatch.

Toy Boat