I tried to read just about all posts (only the movie names 
Here are some objections:
Somebody mentions “Snatch”. Oh boy. To call it a worst-movie-ever needs real dedication not to like movies at all, and cannot solely be explained by personal taste. Snatch is one of the best movies ever in my list. It may be even “bad” for some, but worst???.
Somebody else mentions Robocop 2 and 3. I agree with 3. CRAP beyond belief! But 2, no. It was a good one, that just didn’t live up to the legendary Robocop 1.
Now: My 1 or 2 bits, I won’t come up with 30 movies, but a few with “almost” reasonable reasons 
Bad, and don’t watch:
Romy and Michele’s High School Reunion-
Oh my. The plot and the messages given between the lines made me wanna puke. -spoiler start- In the end the popular girls and boys of high-school all marry poor husbands and wives and continously make children. The two stupid woman find rich partners, whom at first they don’t like at all and make fun of at the reunion party, but once they learn how rich they are, they have a sudden change of heart, and this is supposed to be a good thing -spoiler end- Also, there were so many little bits that drove me mad…
Bad, but see it for yourself:
Vertical Limit-
So many inconcistencies within itself. Visually stunning. That’s why it deserves to be on this list. You have so good visuals and you ruin it completely with an awful scenario: if you do the wrong thing like I did and start thinking wisely during the movie, you cannot enjoy the visuals anymore.
Bad, see it for yourself:
Independence day-
I’ll get past the U.S. propaganda, it is so obvious that it is not dangerous (doesn’t secretively do it like in loads of others)
B]-spoiler start-[/B] But the moment they “uploaded” a virus in the mothership of the E.T’s, I felt awful. This not only means they have fully reverse engineered their operating system including network protocols and their assembly code (or maybe they just compiled with Borland
), but also found the necessary security holes to upload the virus, argh… -spoiler end- I couldn’t get past this.
Good movie with the worst ending:
Signs
You make a movie that does thrill and make people wonder till the end, and then you shock them with the stupidest of endings: -spoiler start- Creatures who get burned instantly by the most abundant element on earth which they are trying to overtake, who are clever enough for inter-stellar transport, but have the awful habit as exhibitionism (they simply go naked in public :=), and they can’t leave this habit even on earth so we can spray’em death with a simple hose -spoiler end- Oh boy. I felt betrayed and frustrated at the end of it. Imagine one of’em caught in rain. Which does happen quite often in our beloved planet.
Worst, everybody should watch it, bar none.
Dunyayi Kurtaran Adam-
I come from Turkey where the worst of the worst emerged :“the man who saved the world.”. This is movie so bad, that it became a cult movie. Really. Actually, it is so at the extreme of being bad, that you don’t need to call it “bad”, just like you don’t think when you are breathing. Everybody needs to see this.