Old Effects That DON'T hold up.

[JaseSF]

Unknown Island comes to mind although I do have a bizarre fondness for those dinos in some sense just like I have even more fondness for The Brain From Planet Arous and The Giant Claw. Bad as they are, at least they did seem to have personality.

http://www.badmovies.org/movies/unknownisle/

[Leah]

The death scenes for The Knightrider and Goose in Mad Max 1
http://www.youtube.com/watch?v=P7Bcov5SGU0
http://www.youtube.com/watch?v=DbTc8v0Y58w&feature=related(2:47)
The cartoonish eyes popping out is terrible

[diamondwaspvenom]

1) Bruce the shark in Jaws 2, 3 and 4 looks pretty fake.

2) In Nightmare on Elm Street 2, there's a scene with an encounter with dogs that have human faces. One could obviously detect that they're just dobermen with rubber masks.    

3) Jason Voorhees kills someone in Friday the 13th part III by squeezing his head to the point where his eye pops out. It's pretty clear that the head is phony and the eye popping out looks silly.

4) The Creeping Terror, do I have to explain this one?

[Trekkie313]

The Special Effects in Star Trek 5 are pretty weak.
Paramount decided not to go with ILM for some reason...
Heck what am I saying. The whole movie was pretty weak!

Actually, they couldn't because they were booked solid with other projects at the time.

[JaseSF]

Monster From Green Hell has some pretty darn slow-moving stop motion giant bugs...

[Doggett]

The head scene in Dead and Buried.
Even at the time the film-makers thought it was rubbish...

[Trekkie313]

The head scene in Dead and Buried.
Even at the time the film-makers thought it was rubbish...

The doctor being filled with embalming fluid. Yeah, it sucks.

[Raffine]

The muppets in RETURN OF THE JEDI look and act just like what they are: muppets.

[AndyC]

The muppets in RETURN OF THE JEDI look and act just like what they are: muppets.

Agreed. And I always thought the pig guards looked like they should be roaming an amusement park or clowning for sports fans. The costumes looked like costumes.

I think somebody has mentioned lightning that's drawn on in post-production. I just watched Godzilla vs. Mechagodzilla again the other day, and even for a Godzilla movie, it's got an insane collection of drawn-in forcefields, rainbow energy beams and cartoony zigzag lightning bolts. Yet, none of this looked the least bit phony to me as a kid.
http://www.youtube.com/watch?v=X3TSmbMD5ng&feature=related

[Leah]

THIS:

no comment.

[Mr. DS]

The muppets in RETURN OF THE JEDI look and act just like what they are: muppets.

Well put and well deserving.  You know what though, I kind of prefer the Muppets compared to the deplorable CGI number they inserted in Jabba's Palace in the special-ed edition. 

[ChocolateChipCharlie]

It's not really an effect, but the face Norman Bates makes at the end of Psycho, during the "reveal" scene, during the knife wrassle always bothers me.  The movie is essentially perfect otherwise, but I just don't buy that face he's making and it bugs me.

This isn't exactly the face I mean, but it's right after this (couldn't find a pic of exactly the one I'm talking about):

[Umaril The Unfeathered]

Unknown Island comes to mind although I do have a bizarre fondness for those dinos in some sense just like I have even more fondness for The Brain From Planet Arous and The Giant Claw. Bad as they are, at least they did seem to have personality.

http://www.badmovies.org/movies/unknownisle/

Yeah, The Brain From Planet Arous had personality, his name was John Agar 

Seriously though, the movie did have a bizarre quality to it. Enough that I watched it almost every time it came on WNEW 5's Creature Features.

[AndyC]

The muppets in RETURN OF THE JEDI look and act just like what they are: muppets.

Well put and well deserving.  You know what though, I kind of prefer the Muppets compared to the deplorable CGI number they inserted in Jabba's Palace in the special-ed edition. 

The muppets from ROTJ and the Killer Shrews have me wondering whether it counts if the effects were never convincing to begin with.

[Umaril The Unfeathered]

The muppets in RETURN OF THE JEDI look and act just like what they are: muppets.

Agreed. And I always thought the pig guards looked like they should be roaming an amusement park or clowning for sports fans. The costumes looked like costumes.

I think somebody has mentioned lightning that's drawn on in post-production. I just watched Godzilla vs. Mechagodzilla again the other day, and even for a Godzilla movie, it's got an insane collection of drawn-in forcefields, rainbow energy beams and cartoony zigzag lightning bolts. Yet, none of this looked the least bit phony to me as a kid.
http://www.youtube.com/watch?v=X3TSmbMD5ng&feature=related

You bring up a good point, Andy. It brings up a point about the 1966 Ultraman TV series.

The son of Toho man Eiji Tsuburaya (Akira I believe) owned Tsuburaya productions, who wasted no time trying to outdo Toho's FX. They went and bought an optical FX printer, and were the only other studio in the world to own one besides Disney.

That said, here's a small clip of Ultraman 1966 as he fights a creature called Ragon. Note the improved quality of the beams from both Ultraman and Ragon, due to said optical printer.

http://www.youtube.com/watch?v=_vxaDxUg7Dg