Wonder Boys. Not sure if it’s underrated. It’s just not well known. One of my favorites.

Cloud Atlas! Third time watching it and still picking up clues ?

Brazil. (Terry Gullium of Monte Python directed, with a cameo by Robert DeNero.) Post modern apopalictic.... not unlike our world today.

Shutter Island... one of DiCaprio’s more underrated films, with a great twist.

Cloud Atlas... the way the scenes intercut in very short segments makes it hard to follow but on repeated viewing I enjoyed it very much, a lot of excellent performances.

I enjoy Tombstone. Val Kilmer's Doc Holliday is incredible.."I'm your huckleberry"

There's history, humor, incredible friendship/love relationships and tragedy.

Bless the Beasts and the Children was one I saw as a Late movie maybe even before cable was widely available.

It is a bit cheesy in places, but the story is solid and moving. Also the title song by Karen Carpenter opens the face faucets.

The Last Boy Scout. Great buddy movie.

The Matrix Trilogy.

These movies in my opinion are perhaps the best. It makes you question your own existance. The level of technical detail in these movies is amazing. Seemingly everything has a valid explanation - from the storyline, to the stunts. Every time I watch it, something new is revealed to me..

Agree on Gattaca, my high school biology teacher showed it to us.

Right now for new movies, Nicolas Cage's new flick Mandy was epic if you like ridiculous sci fi, campy grindhouse revenge, Terantino, Hunter S Thompson and 80s nostalgia. Stunning cinematogtaphy, great soundtrack, just the right amount of action, drugged up weirdness and scenery chewing.

Eternal Sunshine of the Spotless Mind
Hedwig and the Angry Inch
Red State and Tusk (Kevin Smiths horror flicks)

More campy horror/comedy:
Tucker and Dale vs Evil
Zombeavers

Gattaca is awesome and I've got to agree with Hot Rod and Mr. Brooks from the comments.
I'll add...
Troy
Night Crawler
Casino Royale
Prisoners
Kingdom of Heaven
American History X
The Prestige
Jerry Maguire
Not the most obscure list but they are all great movies and at the very least underhyped.

Storm of the century.

Once in a while it's nice to see a movie without the tiresome clichés of, for example, the good guy charging mindlessly at the problem and win only because he is lucky.

Didn't like Gattaca myself. I can see why some people do, but it hits a few points too hard and has some inconsistencies that ruined it for my often overly critical self.

Space Cowboys

Legend of 1900

Just watched again a recent Keanu Reeves movie, with Winona Ryder, "Destination wedding."
Released this year and already on amazon.

It is a rom-com, my fave. It seems to be a stageplay, lots of non-stop dialog. But, it is consistent in humor and deliver. As are the actors. Seems a bit stiltled at first, but it delivers, until the last scen's very slight shrug.

I am happy that Keanu is doing these little movies. He and Winona are there during the whol movie.

TOo many rom-coms started turning to starch near the end/climax.

And, of course, the second time through was just as good.

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Another one: Henry's Crime from 2010 keanu and james caan. Got some WTF gems over and over.

I have an XL sheet with a over a hundred movies, and TV, and plays, that we have enjoyed and rated.

If you have not seen "Waking Ned Devine" you have no idea what it is to love. A great movie and one of the best climaxes ever.

When I saw this post this film sprang to mind. My selection is no where near as good as most of the other films named here but when i watched it I was surprised and thoroughly entertained. The film is under rated everywhere including imdb and rotten tomatoes. Deep Star 6 -1989 if you like a good monster flick watch it!

My most underrated movie is The Messenger: The Story of Joan of Arc by Luc Besson, starring Milla Jovovich, John Malkovich, Faye Dunaway, and Dustin Hoffman.

Searching and upgrade

Solaris. Do we remember how things were or how we want them to be?
Both versions.
And the book.
Hmmmmm I may be a Solaris geek!