If you're at all confused about familial relationships, like I am, then you'll appreciate this chart showing how cousins are related. Surprise everyone at your next family reunion!

Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo

Wikipedia says this sentence is grammatically correct for all sentences consisting of at least one "buffalo" (using Chompskyan theories of grammar).

Bonus linguistics post: Yuen Ren Chao's poem "Lion-Eating Poet in the Stone Den"

(Thanks lonelysandwich!)