The Sixth Sense - fuck, I have to watch this again to confirm, but it probably is in fact the worst movie ever made.
Ghost
Armageddon
Harry Potter and the Philosopher's Stone
Zoolander
Showgirls
Godzilla (1998)
A Sound of Thunder
Deep Blue Sea - practically the only pleasing thing about this film is seeing Aida Turturro's character die.
The Giving Tree - a.k.a. Shaded Places or Brutal Truth. So bad they renamed it twice to try and save it. A copy of this was in the DVD player in my apartment when I moved in, haha.
Mystery Science Theater 3000: The Movie. A pet hate of mine for years. It was an extremely poor introduction to MST3K that put me off checking the show out any further until recently. I don't know why it was passed off as a movie when it's just another episode of the show. As a TV show, it's a cute way to watch silly old movies, and it's not so bad if the episodes are hit-and-miss. But to actually rate the MST3K Movie in itself... it's basically equivalent to having a few friends come over, sit on your couch and make a bunch of dumb toilet jokes, 5% of which you find funny. This Island Earth was a groundbreaking and spectacular film in its day, and MST3K didn't rise to the occasion for their 'Movie' at all.
There's also a dull movie I saw about 16 years ago that I can't remember the name of. It was a romantic drama where 3 or 4 guys at a cafe/bar spot a group of ugly women at another table and dare each other to date them as a joke. One guy falls in love with a chubby woman anyway, but then she finds out about the dare and he has to try and win her back. It looked like a straight-to-TV American film from the early 1990s. I think it had "dog" in the title, because they describe the women as dog-ugly. I even downloaded IMDB data and looked into 100s of titles but haven't found it yet. Even if I did, the chance of finding a copy to watch is practically zilch.
I guess you've gotta love their tootin' accents or it's not real good huh? Aww geez.