Not necessarily in any order:
Pulp Fiction - Various seedy underworld types including a boxer (Bruce Willis), hitmen (John Travolta and Samuel L. Jackson), a mob boss (Ving Rhames), the mob boss' wife (Uma Thurman), and an assortment of other weirdos have their lives intersect in Los Angeles.
The Big Lebowski - The Dude has his rug urinated on by a couple henchman looking for a guy with his same name and he goes on a sacred quest to receive restitution for said rug. (Jeff Bridges, John Goodman, John Turturro, Steve Buscemi)
Goodfellas - Years in the lives of a New York mobster and his buddies ( Ray Liotta, Robert DeNiro, Joe Pesci)
The Dark Knight - Batman/Bruce Wayne (Christian Bale) tries to balance his alter egos and battle the Joker (Heath Ledger) for the soul of Gotham City (Michael Caine, Maggie Gyllenhall, Morgan Freeman, Aaron Eckart, Gary Oldman)
Anchorman: The Legend of Ron Burgundy - News Anchor Ron Burgundy (Will Ferrell) copes with fame, diversity, the "f word", and women's liberation in 70's San Diego (Paul Rudd, David Koechner, Steve Carell, Cristina Applegate)
The Departed - An undercover cop (Leonardo DiCaprio) and a mob boss' (Jack Nicholson) mole (Matt Damon) try to smoke eathother out in quiet city Boston. (Alec Baldwin, Mark Wahlberg, Martin Sheen)
L.A. Confidential - Three cops in 1950's Los Angeles (Russell Crowe, Guy Pearce, Kevin Spacey) try to untangle a web of murder, sex, and corruption. (James Cromwell, Danny DeVito, Kim Basinger)
Iron Man/Iron Man 2 - The origin and further exploits of one of the coolest superheroes of all time. Tony Stark (Robert Downey Jr.), a billionaire playboy and head of Stark Industries, the world's biggest weapons manufacturer, juggles his alter ego, saving the world, and having a really hot secretary (Gwyneth Paltrow)
The Godfather - The story of the Corleone family and it's patriarch (Marlon Brando) and how his youngest son Michael (Al Pacino) inherited the throne. (James Caan, Robert Duvall, Talia Shire)
Inglourious Basterds - Once upon a time in Nazi occupied France, a group of Jewish American soldiers led by a good ol' boy from Maynardville, TN (Brad Pitt) terrorize the Nazi's with scalping and a huge dude with a baseball bat. (Eli Roth, Diane Kruger)
Hope this helps a little.