QUOTE(Lt Ripley)
you must have missed my post about the 'nessie ' photo
Indeed pardon me

There is a lot of hoax in the paranormal world but to me it's idiots having fun so I don't give them too much importance. The most famous I think is the alien autopsy film witch was supposed to come from Roswell.
About cold fusion It could be real, but what happended in 1989 was a real blow to the scientific world. It was a huge story in the media all around the world for months while in fact they were'nt ready to publish at all. The main problem was the obvious mistakes in their early papers and the difficulties for others to repeat the experiment. It took pretty much 15 years for people to be convinced, and it's not really what people were thinking while imagining cold fusion.
The backlash probably ended up worst than the mistake done by Fleischmann and others but it will stay as a huge mistake, if not a hoax.
I did'nt know much more than my souvenirs as a 9-10 years old

But it's the first thing that came to me while i was searching for an hoax.
From wiki, just to show how fast things can change:
"On April 12, Pons received a standing ovation from about 7,000 chemists at the semi-annual meeting of the American Chemical Society. The University of Utah asked Congress to provide $25 million to pursue the research, and Dr. Pons was scheduled to meet with representatives of President Bush in early May.[51]
On May 1, the American Physical Society held a session on cold fusion that ran past midnight in which a string of failed experiments were reported. A second session started the next day with other negative reports, and 8 of the 9 leading speakers said that they ruled the Utah claim as dead. Dr. Steven E. Koonin of Caltech called the Utah report a result of "the incompetence and delusion of Pons and Fleischmann". The audience of scientists sat in stunned silence for a moment before bursting into applause. Dr. Douglas R. O. Morrison, a physicist representing CERN, called the entire episode an example of pathological science.[52][53]"
EDIT: A lot of fun Hoax can be find in the Hoax section of Wikipedia:
-Idaho, the northwestern US state, was named as the result of a hoax. Lobbyist George M. Willing suggested the name, claiming it was a Native American term meaning "gem of the mountains." It was later discovered that Willing had made up the word himself. As a result, the original Idaho Territory was renamed Colorado. Eventually, the controversy was forgotten and the made-up name stuck.
-Rosie Ruiz finished first in the women's division of the 1980 Boston Marathon by riding the subway to a point near the finish line and jumping back into the race. Her marathon title was revoked when the hoax was discovered.
-In April, 1985, Sports Illustrated ran a profile written by George Plimpton of an amazing new pitching prospect for the New York Mets named Sidd Finch. Finch was a student of yoga ("Sidd" being short for "Siddhartha") who had studied with Tibetan monks to perfect his pitching and claimed to throw a 168 mph fastball. The Mets helped with the initial story but the magazine admitted to the hoax on April 15.
Nothing of great history significance but some fun stuff!