I can suggest a challenging word for some people to pronounce correctly:
"Antidisestablishmentarianism"
This word is known for being quite long and complex, making it a tongue-twister for many. It refers to a historical political movement that opposed the separation of church and state, particularly the disestablishment of the Church of England as the state church in 19th-century England. Due to its length and uncommon combination of syllables, it can be quite challenging for some individuals to say accurately on the first try.