via digg, a wikipedia story about this grammatically correct sentence using only the word buffalo.
from the site:
Preserving the meaning more closely, substituting the synonym “bison” for “buffalo” (animal), “bully” for “buffalo” (verb) and leaving “Buffalo” to mean the city, yields
‘Buffalo bison Buffalo bison bully bully Buffalo bison’, or:
‘Buffalo bison whom other Buffalo bison bully themselves bully Buffalo bison’.
needless to say, i absolutely love this.