There are to many to list. I would recommend checking out the designingsound.org website, check out the featured sound designers page, http://designingsound.org/featured-sound-designers/, and research the movies they worked on using http://www.imdb.com. That is where I would start. Also check out http://www.filmsound.org, another great resource...
Here are a few of my favorites heavy-hitters off the top of my head:
The Matrix Trilogy - Dane Davis and his crew are masters of passive sound design; you know the sound is designed but the sound is so good you "know" its real.
Star Wars - The movie that started modern sound design.
Wall-e - The best movie ever made, in my mind, that tells an amazing story with sound, not dialogue.
Jurassic Park - A great movie. I love that the sound for this movie was so large and defining using the techniques that we use today, but where revolutionary at the time.
The Hulk - A friend of mine was on this project and shared some of the horror stories he and the team encountered while dealing with the acting talent and executives as they tried to "help" in the sound design. The fact that the movie turned out sounding so good is testament to the great leadership on the supervisors part.
Avatar - 3 years of sound design and it sounded amazing. I was able to get lost in the alien jungles. Loved it!
Das Boot - Great sound from a movie that is 30 years old.
Fracture - An amazing example of a talking heads movie. The sound was present but extremely passive; did not steal the spotlight from the story...