#1: Homeopathic Flu Remedies
http://moneyland.time.com/2011/08/19/12-things-you-really-should-just-stop-buying/
(via http://www.facebook.com/jamesrandi )
I'd say ANY flu remedies. They don't really work. Only symptoms like pain or fever can be treated whereas treating fever might not always be the best idea as long as it is not very high.
Auto Service Warranties they are just scam, I still buy lottery tickets though you never know when your luck strikes.
i think tamiflu is effective though