I recently watched
The Revenant
. I assume that the bear attack scene was created using CGI. In any event, however it was accomplished, the initial bear attack is currently my all-time favorite special visual effects scene. I couldn't take my eyes off the screen; I couldn't believe my eyes. I've watched the scene a couple of times since and find it more difficult to watch than the first time, which is a curious phenomenon because usually a person becomes desensitized to the sight of violence.

Jurassic Park had the most impressive realistic effect for me (the T-rex leaving the fence).
But the ones that I consider the most exciting in the story would be the skeleton fight in Jason and the Argonautsor anything King Kong did in the 1933 film.
The effect that gave me the biggest wow as a kid was when Clark Kent kicked the football into the sky in Superman the Movie.
The Asteroid chase in ESB was also amazing.
Before JP, the water creature in the Abyss was the most amazing spfx technical jump where it could make human faces.

Blade Runner. Its a work of art & was a lot of work

I would go with avengers. I think 90% of the film has special effects. But i love this movie and catch it anytime whenver it is being aired on HBO.

Definitely the best use of special effects of all time is Jurassic Park.

Interstellar. I need not talk much about it. It's new, so anyone hasn't yet listed the movie here yet.

For some reason, I have always been obsessed with the "Walking Through Walls" effects ever since
4D Man
http://www.imdb.com/board/10052530/?ref_=fn_al_tt_1
.
I will search endlessly for movies with this effect. I just love the look of a well done wall walk!
Scott, there may be side effects of this we don't know anything about

Opeing the Ark in Raiders

Who Framed Roger Rabbit (1988)
Volker Flenske: (While torturing David) I don't know why you're doing this to yourself!

2001- spaceship entering other spaceship with the Blue Danube in back ground - perfect

If I had to name just one special effect, probably the exploding head in Scanners. I'm not a huge fan of the movie as a whole but I really love that exploding head.

the baby in the bath in A Beautiful Mind. I didn't realize it was an effect until I watched some of the extra features on the DVD. I admire Forrest Gump, that would have taken an immense amount of work, Apollo 13 is another fine example. Jarhead has some good ones.
I prefer movies which use special effects to enhance or complement the story, rather than being the actual story, if you get my drift.

Citizen Kane
2001
Brokeback Mountain
Steven Bradford
Seattle WA
http://www.seanet.com/~bradford/

Jurassic Park no doubt about it great mix of special and visual effects! Also POTC Davy Jones is amazeing.

Total Recall
Starship Troopers
Terminator 2
The Fly (1986)
Then some oldies:
Metropolis (1927)
King Kong (1933)
Bride of Frankenstein (1935)
Most Harryhausen features, but particularly First Men in the Moon (1964)
I've got to be missing something.

Dragonheart(1996) Draco is still the most realistic dragon up to date
All of the Lord of the Rings trilogy.
Pirates of the Caribbean: Dead Man's Chest and At World's End(2006 & 2007)Davy Jones and his crew. The Maelstrom battle

Pirates of the Caribbean: Dead Man's Chest.
Davy Jones (as well as the rest of the movie) looks amazing.

Superman: the Movie. Superman flies off as the camera pans to Clark Kent entering Lois Lane's apartment. A brilliant split screen sequence that almost no one notices until it's pointed out.
"Black and white cat . . . black and white cake." - Charles Chazen.

Empire Strikes Back, if I had to pick one the walkers are absolutely awesome, and the sheer intensity of the chase in the asteroid field always get me.
With the Battle of Hoth, there are so many great touches to the AT-AT's movements- it is not 'just' the spectacle, the FX really work hard to propel and enforce what's going on in the story. The slow, thudding approach of the nigh-invulnerable walkers is captured perfectly, and you catch the same feeling of creeping dread the rebels must be feeling.
Good stuff!
'The original Kong seems quicker.'
'Yes, but my Kong won't tire.'

Special Effects (Generally): Star Wars
CGI: Terminator 2 or Lord of the Rings: The Two Towers
''This is good. Isn't it?''

the thing , jurassic park and Terminator 2 all still hold up today.

The Thing and jurassic park
No matter how many sea lions are killed each year by sharks, it never seems like enough

People should look into it.
I think that's a funny thing to say.
I have no idea why!
God made procreation; the Devil made it fun.

"Jurassic Park" is the only one that still looks good to me.
I have no idea why. People should look into it.
"Titanic" still looks good after 10 years as well, but you have to give it to them, they had an actually sinking replica.