Guido's pit stop is without a doubt the Crowning Moment of Awesome for this film. The reaction of Chick Hicks' pit crew is priceless - they drop their mustache grilles. "Peet stop."
Lightning muttering to himself about his failed use of Doc's advice.
Lightning: "Turn right to go left"...Guess what? I tried it, and you know what? This crazy thing happened - I went right! Lizzie: You keep talkin' to yourself, people will think you're crazy. Lightning: (sarcastically) Thanks for the tip. Lizzie: What? I wasn't talking to you.
Lightning's Freak Out when Van and Minny quickly flee Radiator Springs, while he's stuck to Bessie, flailing around:
Lightning: Don't leave me here! I'm in Hillbilly Hell! My IQ is dropping by the second!! I'M BECOMING ONE OF THEEEEEEEEEMMMMMMMMMM!!!!!!!!!!!
Bonus point when you realize that he does become one of them by the end of the movie.
The very final scene after the credits, where Van and Minny are lost in the desert.
(Van and Minnie are in the middle of the desert, dusty, still looking for California)
Minnie: [exhausted] Oh for the love of Chrysler, Can we please ask someone for directions?
Van: [hysterical] NO! There's another ramp close! I KNOW IT! I CAN FEEL IT! HA HA HA HA HA HA HA HA HA HA HA HA HA HA HA!!!
Every morning, Sarge Sarge is raising the flag while playing "Reveille" and Fillmore is playing Jimi Hendrix's rendition of "The Star-Spangled Banner" loudly next door:
Sarge: Will you turn that disrespectful junk off?!
Fillmore: Respect the classics, man! It's Hendrix!
Really, Mater provides pretty much all the Funny in this film.
Mater gets some drinks for Lightning at the free bar in Japan. Those who tried their first "pistachio ice cream" knows what's coming a mile away.
Sushi vender: My condolences.
The scene where Mater actually freaks out after seeing a car with headlights for eyes in Paris.
What made this scene is that this is seemingly a reference to the decision to avoid that sort of character design during development of the original Cars as it made characters look like "snakes".
He tries to crash Lightning's and Sally's date at the Wheel Well by posing as a waiter. He even tries a drink at one point, hates the taste, nonchalantly spits it back out into the cup, then almost serves it to Lightning!
While tearing through Radiator Springs on his new jet engines, he comes across the car he towed in the beginning of the movie. He tows him to the shop, hooking him so fast he pulls him right out from under the dust he'd accumulated.
This little bit during the phone call on TV.
(Francesco Bernoulli is a guest on Mel Dorado's TV show; Mater called in to argue with Bernoulli, and McQueen takes the phone)
Lightning: [over the phone] Yeah, hi, this is Lightning McQueen.
Francesco: The Lightning McQueen, eh?!
Lightning: Look, I don't appreciate my best friend being insulted like that.
Francesco: McQueen, that was your best friend? Ohhh... There's a difference between you and Francesco! Francesco knows how good he is. He doesn't have to surround himself with tow trucks to prove it.
Lightning: You know, those are some strong words coming from a car that is so fragile.