The old man the boat.
The man who whistles tunes pianos.
The cotton clothing is made of grows in Mississippi.
The horse raced past the barn fell.
James, while John had had "had", had had "had had"; "had had" had had a better effect on the teacher.
And last, but not least:
Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo.
How many times do you have to read them to figure out what they're saying? Look it up at wikipedia if you need help.