We used to have to do tongue twister all the time in Drama class.
Some of my favourites were:
Six grey geese in the green grass grazing, grey were the geese and green was the grazing
A lonely lilly lying all alone along a lonely lane
Does this shop stock short socks with spots?
Windingly wound round the wrong wood wool winder, wool wouldn't rewind rightly round the right wood wool winder
the Lieth police dismisseth us