In no particular order:
Pontiac Aztec- universally hated by nearly everyone and a symbol of GM's perverted view of what a new Pontiac should be.
Chrysler Sebring (2007-2010)- Chrysler takes America's favorite convertible and trashes it. The build a sedan that embodies everything wrong with Detroit as the company is sliding into the abyss.
Smart - Nobody can sell more than a couple dozen in their market before be people question why anyone would buy one.
Saturn Astra - GM's costly experiment to bring a competitive small car here from Europe. They give a car that is ready to be redesigned in it's home markets to a US division that built its reputation of cheep (cheeper than this) small cars. The car was too old and too expensive to be an entry level Saturn.
Pontiac G3 - The car Pontiac enthusiast lose sleep over at night. An awful car, rebadged to give Pontiac owners one last kick in the gut before killing the brand.
Lincoln Blackwood/etc- There simply were not enough farm owning pimps to make this a viable product. That might not be a bad
thing.
Honda Accord Crosstour - Seriously.....Honda you had mojo and its gone.....so far gone.
GM's Redesigned MiniVans (2005)- Trying to find one that didn't start life as a fleet vehicle is a proverbial needle in a haystack. Good thing they only lasted a couple of years...Pontiac, Buick, and Saturn already had enough trouble finding customers without these things.
Chrysler Crossfire- Who knew customers didn't want an old Mercedes with bad Chrysler styling...I'm sure Chrysler dealers love servicing these things since parts are hard to find and they share nothing with other Pentastars.
Cadillac STS- Caddy built a competitive Sports-luxury sedan but everyone had stopped paying attention after 20 years of FWD Sevilles.