There are so many but they must be classified:
Hidden Political Agenda's:
Any of the "Billy Jack" movies
Red Planet Mars (Peter Graves, Andrea King, 1951)
RPM is homage to the HOUAC hearings an there are numerous things in this film that are actually sick concepts.
The Atomic City (Gene Barry, Lee Aaker,)
TAC is always billed as a science fiction and yet it is in fact an anti-communist crime drama involving kidnapping and
efforts of U.S. Government Law Enforcement Agencies to save the life of the child and the secret of the Atomic Bomb
Bad Acting
Anything with Zsa Zsa Gabor
Anything with Mamie Van Doren
Bad Writing
Anything Based on a Steven King Novel
Where did they find funding for this trash:
Napoleon Dynamite
Supernova (With Lou Diamond Phillips there are two movies with this title)
Onion Head (Comedy from the 1950's where they tried to capitalize on Andy Griffith's popularity after No Time for Sergeants and fail miserably)
Could have been great if they had found enough money to make the film:
The Phantom From Outer Space. The script was really strong but because one could shoot for free inside Los Angeles Parks in the 1950's most if this was shot in Griffith Park and the rest at the old Francescan Tile Plant in Atwater nearby. Actors are 4th string and do the best they can but no money is still no money.
Spacemaster X-7 The script was really good, but the budget was so low as to make production difficult. The special effects are so abysmal that they are even bad for the levels of technology available in the 1950's. You go away wondering what could have happened with this if they had been able to infuse about $350,000 in 1958 dollars.
It Conquered the World This was one of the films that Peter Graves probably would not have wanted to admit to having been in. Lee Van Cleef and Beverly Garland have roles in this film. It had potential to be decent, but, the entire film completely dies when we are introduced to the most obviously rubber inverted carrot that one could ever meet. As it attacks it's victims they have to pull it's tentacles around them and really try acting to be convincing. Could have been far better with an infusion of money.
Target Earth This was the film on which "Mars Attacks" was loosely based. The problem here is that again if money had been in place it could have been great. The laughable special effects completely killed a basically good script. "Mars Attacks" using the singing of "Slim Whitman" to destroy the creatures was not far from the original premise. It is sad that the money or lack of it relegated a decent script into a joke.
Incomplete and Bad Story Line because so much of it was left out of the movie:
Alien
Worst Science Fictions:
Remake of The Day the Earth Stood Still with Keanu Reeves insults the original great film done by Robert Wise.
Remake of The Thing by John Carpenter was poorly done and was confusing. It did follow the Campbell Book, but the execution was lousy.
Remake of The War of the Worlds with Tom Cruise. No redeeming qualities
Remake of Invaders from Mars did not have the original fear factors that the original did.
The Giant Claw: This movie is so bad it makes Plan 9 From Outer Space Look like absolute movie making genius. Wait until you see the creature and the special effects. If they couldn't do it anywhere near right, why do it at all.
The Killer Shrews: James Best at his worst before he became Sheriff Roscoe P. Coltrane on the Dukes of Hazard. This had very little to recommend it.
Worst Action Films
Any Rambo
Any of the "Walking Tall" Movies
Remake of Gone In 60 Seconds
Any of the Fast and Furious Movies
Tomboy
Any Movie Involving Street Racing