Many great ones have been named... A few of mine, in no order:
Buying the Cow (Possibly the funniest Ryan Reynolds movie out there)
Waiting (Darn close to Buying the Cow)
Empire of the Sun (that Mustang scene? C'mon now, tell me you haven't rewound and rewatched that a million times).
Monty Python Holy Grail
Monty Python Life of Brian
Monty Python Meaning of Life
Erik the Viking
Little Miss Sunshine (Sister brought that home this winter break, and I had to buy a copy myself. Hilarious)
Pulp Fiction (Arguably the most innovative movie of its time)
A Very Long Engagement (Audrey Tatou (sp?) is just a great actress)
India Jones Trilogy
Original Star Wars Trilogy (the new ones are fancy, yet poor IMO)
Butch Cassidy and the Sundance Kid (Are you kidding? The fall alone will kill ya!)
Jaws
Braveheart
Last of the Mohicans (Great soundtrack)
The Blue Max
The Hunt for Red October (Or anything Sean Connery is in, really)
Band of Brothers (Like someone else said, does this count? At any rate, best WW2 movie-ish thing out there)
SLC Punks
Battle of Britain (I love the Polish pilots scene)
Forrest Gump (This one could be my favorite. Certainly one of the best movies ever made)
Also, I enjoyed "The DaVinci Code," but I've never read the book, and that's probably why.