Fear of failure must never be a reason not to try something.

Well its said that we learn from our failures and next time we try and improve ourselves the next time we do the same thing. Hence lets have a keen look at global level flops in various fields
Flops in television
The disastrous 1980 season of Saturday Night Live
The BBC soap operas Triangles and Eldorado
Supertrain
Pink Lady & Jeff
Bette
The Chevy Chase Show
The Pat Sajak Show
Thicke of the Night - Talk show with Alan Thicke
The third season of Big Brother
Turkeys (Flops in theatre)
1600 Pennsylvania Avenue (1976) Lyrics by Alan J. Lerner, of "My Fair Lady" and "Brigadoon" fame; music by Leonard Bernstein, with important Broadway successes such as "On the Town," "Candide," and, most notably "West Side Story" to his credit
Closed after only seven performances There was no cast recording made. An attempt was made to revive it in London in 1997. A reviewer commented "As exhumations go, this one had its bright moments."
Flops in film
A movie is most likely a flop if it doesn't perform as expected. A major movie flop might barely (or not even) make back the money it took to finance it. In extreme cases it might put the studio out of business.
A separate discussion of movie flops provides examples and rationales.
Commercial Flops
Aviation Flops
These are aircraft which were technically sound, but failed in the marketplace. For aircraft which failed to work at all see 'Flops in science and engineering'.
The Convair CV-880 and CV-990 - these aircraft were commercial disasters as they only offered five-abreast seating, and were easily outcompeted on price by the Boeing 720 which was based on an existing aircraft type.
Supersonic transports: Boeing 2707, Tupolev Tu-144, arguably Concorde
The Dassault Aviation Mercure - this aircraft had extremely limited range and as a result only ten were built for the French domestic airline Air Inter
The Northrop F-20 Tigershark - this fighter aircraft was designed as a private venture for export, but failed utterly as foreign air forces wanted the more prestigious F-16 Fighting Falcon used by the USAF, despite the F-20 having superior performance and lower cost.
Automotive Flops
Ford Motor Company's Edsel
DeLorean automobile
Electric cars - Ford Motor Company and General Motors, who only had lukewarm interest in the technology, have dropped production of their electric car models.
Sinclair C5 - a battery powered car designed by Sir Clive Sinclair
The Bricklin SV-1
Computing Flops
The IBM 7030, also known as Stretch, was IBM's first attempt at building a supercomputer. Its actual performance was less than one third of its original specification. This resulted in IBM drastically dropping the price and losing money on every machine sold.
The ILLIAC IV array processor supercomputer
Microsoft Windows 1.0 was a huge flop because its sales were low, it was very slow, needed a lot of memory for the time, and practically no software was ever written for it.
Microsoft Bob.
Apple has had flops, notably the Apple III, Apple Lisa, and arguably the Apple Newton.
IBM had the IBM PS/2 and the IBM PCjr
IBM's 4" diameter floppy disk drive, introduced at about the same time as Seagate's 3" floppy, Hitachi's 3.25" floppy, and Sony's 3.5" floppy. (All but Sony's flopped).
The Commodore Amiga was a flop in the United States (but was successful in Europe).
Amiga CDTV - This early multimedia computer was overpriced and suffered from using the obsolete AmigaOS 1.3, when version 2.0 was already available.
Data Play CD replacement disk technology Cited by Jim Louderbeck as one of the "eight biggest tech flops ever"
Go (pen computing corporation), cited by Jim Louderbeck as one of the "eight biggest tech flops ever".
Intel expected the Itanium processor (referred to by detractors as "the Itanic") to revolutionize the microprocessor industry, but after 7 years of development and billions of dollars spent the first Itanium chip proved an utter technical and commercial failure. However the project still goes on, and Itanium 2 is an improvement.
Iomega Click! Drive. Cited by Jim Louderbeck as one of the "eight biggest tech flops ever"
In the 1980s, Commodore International became the first company to sell a million home computers. Hoping to repeat the success of its multimillion-selling VIC-20 and C-64 computers, it released the Commodore Plus/4 in 1984. It flopped. Commodore tried--and mostly failed--for 10 years to duplicate the C-64's success and went bankrupt in 1994.
The INMOS Transputer, a brave attempt at a different way of computing - but now largely forgotten.
WebTV. Internet delivery via television set and set-top box Cited by Jim Louderbeck as one of the "eight biggest tech flops ever"
The Sinclair QL an unsuccessful attempt by Sinclair Research to make a 16 bit computer in the mid 1980s
Video Game Flops
Sega has had numerous flops in North America, for example the Sega Saturn, the Sega Nomad, the Sega Master System II and III, and the Sega 32X. (The Master System was successful in Europe and Brazil, and the Sega Saturn was successful in Japan.) The Sega Mega drive was not well received in Japan.
Nintendo, not to be left behind, has produced the Nintendo Virtual Boy and light gun games.
The Game.com handheld
The Atari Jaguar console and the Atari Lynx handheld
Daikatana, the hyped and massively delayed video game from John Romero
The Atari 2600 version of E.T
The Compact Disc-Interactive (CD-I) player, a "multimedia machine" jointly developed by Philips and Sony. It was considered overpriced and underpowered.
The 3DO Multiplayer, a "multimedia machine” designed by R.J. Mical and the team behind the Amiga and marketed by Trip Hawkins, founder of Electronic Arts. It was introduced at $699, twice the price of most game consoles.