My girlfriend hasn’t seen any Star Wars movies, Star Trek movies or Star Trek episodes.
I haven’t seen the 3rd Matrix movie or any of the Godfather movies.
Terms of Endearment
Taxi Driver
Never seen ET or The Sound Of Music. Deliberately. I have a low treacle-intolerance threshold.
The Godfather
The Sound of Music
Take that back, you philistine! God, is the mordant satire lost on everyone but me?
Boy, I must not get out much. Oh, wait, we all knew that already. I haven’t seen the majority of these movies.
Out of this thread alone, I have never seen:
Half-baked (never even heard of this one)
Office Space
Dead Presidents
Trainspotting
Pulp Fiction
From Dusk Till Dawn
Any of the Matrix movies
Any of the Friday the 13th movies
All but one of the Nightmare on Elm Street movies (don’t ask which one I saw, cause I don’t remember)
The Exorcist
Donnie Darko
Any of the Austin Powers movies
Either Kill Bill (though I saw about 20 minutes of the first one, then turned it off from a mixture of boredom and disgust)
Citizen Kane
Any of the Godfather movies
Fahrenheit 9/11
Schindler’s List
Casablanca
The Usual Suspects
Braveheart
Flashdance
Fame
Terms of Endearment
Taxi Driver (and we even own that one, fercryinoutloud)
Some of them I’ve meant to watch, but never quite found the opportunity, some I just never felt any desire to see, and one (Pulp Fiction) I have actively resisted efforts to get me to watch it. (I don’t enjoy gratuitous violence or weirdness for the sake of weirdness, and my husband knows this. Why he then thinks I would like that movie is utterly beyond me.)
Off the top of my head, more movies that everyone but me has seen:
Roman Holiday
The Birds (I once caught the last ten minutes or so)
African Queen
Rear Window
Sunset Boulevard
The Psycho sequels
Hannibal
There’s about a billion more, but that’s all I can think of at the moment.
Of those mentioned I have seen all but
Half-Baked
Star Wars II and III (well V and VI I guess now). I saw the original and had no desire to see any more but had kids to take when the new ones came out.
Matrix II and III. Again saw the original and enjoyed it but had no desire to find out what happens next.
Star Trek. Only saw the one with a whale in it on TV.
Dumb and Dumber
Not quite movies but…
I’ve never seen Eddie Murphy: Raw or Delirious though I feel like I can quote them both from beginning to end after ~20 years of hearing other people do so.
Not only have I never seen a Star Wars film, I have never seen a Disney movie. None of them 
No-one believes me but I have been deprived of this ‘pleasure’
Wow, I thought I was the only one who hasn’t seen any of the Star Wars movies. I also haven’t seen any of the LOTR or the Godfather series.
But, please, please, for those who haven’t seen it, go rent The Big Lebowski. Best. Movie. Evar.
Dune. That’s the big one.
Usual Suspects
Mallrats
I’ve never seen Forrest Gump. Or the Titanic. Or Shrek 2.
Never saw The Crying Game or Citizen Kane. I’ve heard the spoilers for them repeatedly, so…
I didn’t board the Titanic, nor did I follow the rabbit that leads to Donnie Darko either.
Never seen Almost Famous either, but I really really want to.
And you should keep it that way. You have 6 hours that the rest of us will never get back.
Never seen Reality Bites. That one is supposed to be The Movie That Defined Generation X, too.
Deliverance
Most of the old classics (Gone with the Wind, Casablanca, etc.)
Any of the Godfather movies
Any of the Terminator movies
Most Star Trek movies (I’ve only seen IV and V)
Most popular chick flicks (Sleepless in Seattle, et. al.)
Any Friday the 13th movie
Any Scream movie
The Exorcist
Schinder’s List
Saving Private Ryan
Flashdance
Grease. I’ve caught bits and pieces of it, but have never set out to just sit down and watch it.
The Passion of the Christ
My friends used to go on and on about The Princess Bride, which I still have yet to see.
Galdangit, what’s that Christmas movie that’s aired incessantly every Christmas and stars Jimmy Stewart as a guy who want to off himself? I’m totally spacing on the name. Anyway, I’ve never actually seen that. I feel like I should since it’s part of modern day culture but I know roughly what happens and just haven’t felt like sitting through it…
It’s a Wonderful Life. Good movie, if somewhat heavy on the cheese.