snake oil

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A worthless preparation fraudulently peddled as a cure for many ills.
• noun Speech or writing intended to deceive; humbug.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A traditional Chinese medicine used to treat joint pain.
• noun A type of 19th century patent medicine sold in the United States that claimed to contain snake fat, supposedly a Native American remedy for various ailments.
• noun idiomatic A fraudulent, ineffective potion or nostrum; panacea.
• noun idiomatic Any product with exaggerated marketing but questionable or unverifiable quality.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun (medicine) any of various liquids sold as medicine (as by a travelling medicine show) but medically worthless
• noun communication (written or spoken) intended to deceive