OMG! I watch Good Will Hunting every two or three years because of the dialogue.

Three favorite scenes:
First One:
They buy fast food and then stop the car to pick a fight in a playground.
Casey Affleck: "We just seen the guy 15 minutes ago at the park. If we was gonna fight him, we should fight him then. We got snacks now. "

Second One:
Robin Williams and Matt Damon discuss in detail Game 6 of the 1975 World
Series of the Red Sox vs the Cincinnati Reds, a game that neither one had seen. Williams had tickets but missed the game:
Williams: "I just slid my ticket across the table, and I said, 'Sorry, guys; I gotta see about a girl.'"

Third Scene: Heartbreaking when Matt Afleck convinces Matt Damon to leave town to follow his future:
Matt Affleck: "Look, you're my best friend, so don't take this the wrong way but, in 20 years if you're still livin' here, comin' over to my house, watchin' the Patriots games, workin' construction, I'll kill ya."