This topic is for that particular moment, in the first 1/3 of the film or so, during a movie when you knew what you were watching was something special. I'm talking about a certain scene that, for whatever reason, makes you think that this might be one of your favorite films even though you have not seen the whole thing yet.
My examples:
Star Wars -- The "Ootini!" scene, where the Jawa fires at R2D2 and the sparks crawl and dance about his frame, R2 gives a little squeal, and falls flat on his face. I remember thinking "Wow, the attention to detail even in that little animation says a lot about this movie. And humor in an SF film? This is gonna be great!"
Jimmy Neutron, Boy Genious -- "My clothes don't match! My clothes don't match! I'm out in public, and my clothes don't match!" in a sing-song, wiggly butt fashion. This had me rolling.
Bill and Ted's Excellent Adventure -- Bill and Ted are sitting in the car and Ted expresses real concern about being sent to military school. Upped the level for a bit of real characterization and not just another party-boy movie.
American Psycho -- The business card scene. The humor and absurdity of the one-upmanship here underscored the bizarreness and unreality of the whole flick.
Billy Elliot -- The scene where he's sitting on the edge of the boxing ring, leaning his chin on the rope, talking about his mom. The color and lighting in this scene are amazing. Immediately followed by "I Love to Boogie" showing the joy of dancing.
Stargate SG-1: "Children of the Gods" - It's a pilot, but its feature length, and when I saw it, I thought it WAS a movie. When Jack brushes past Daniel to greet Skaara. I was glad they didn't just have these two as best buddies right from the start. At the end of the Stargate movie, they were friendly, but still hadn't quite forgiven each other. The other scene that cemented my love for the movie/show was when Carter said something about having to MacGyver a system to dial the gate. Humor and actual characters, things that really make a movie for me.
"Raising Arizona" - it's the soundtrack. OK, I admit it, it's the bleedin' yodellin' sountrack that won me over! Once I came to terms with it, the rest of the film was magnificent.
From Dusk Till Dawn when they had a dialogue scene in one continuous shot as Benny’s World of Liquor exploded behind the Gecko brothers than; the bros got into a car, that really killer song came on and they showed them drinking and popping pills while driving down the road. I knew at that moment this was going to be a real bada$$ movie, and not the sanitized for family viewing criminals that Hollywood has been giving us lately.
Pulp Fiction, when Dick Dale's "Misirlou" blasted during the opening credits. Way cool.