Guido changing four tires by himself in about four seconds.
To amplify the awesomeness of this, a professional pit crew who was mocking him just a few seconds earlier can do nothing but watch in Stunned Silence.
It's not as flashy as the tire change, but Lightning McQueen sacrificing the race for The King definitely counts.
Plus everybody (except Chick Hicks) realizing why he did it, and recognizing McQueen as the real winner.
Tex Dinoco: There's more to racing than just winning.
Doc Hudson's drive around Willie's Butte, especially when he turns right to go left.
And don't forget the long-awaited praise he got at the Piston Cup tiebreaker. Pretty much everyone was in disbelief—even Chick Hicks' own pit stop was in awe—and the WHOLE CROWD starts cheering that he was seen.
For the sequel, Mater definitely Took a Level in Badass this time around, culminating in the scene where he deduces Axelrod's involvement and exposes him by forcing him to deactivate his own bomb.
Pretty much any mention of Doc, but especially the new Hudson Hornet Piston Cup
The scene where the residents of Radiator Springs basically curbstomps an entire army of the universe's equivalent of the Mafia.
That scene was pretty awesome, but the part that was the most awesome was definitely Sarge calling up an entire regiment of the British Army to take down the Lemons.
Did we forget Guido removing the mob hoods' wheels in mid-combat?!
In one part of the scene, Lightning, who understands perfectly well that these guys want him dead, shrinks as the Mooks come after him. Cue Mater jumping in front of him and taking on the four comers that attempt to jump his friend. And winning.
Finn's battle against Professor Z and Tony Trihull on the River Thames. Especially Tony Trihull being blown to smithereens by Finn's bombs.
Sarge saves McQueen by switching out the Allinol with Fillmore's organic fuel, thereby preventing the deathray from reacting with his engine. Properly Paranoid indeed.
Mater escaping from a clock tower by letting his gatling guns spool up until the ropes holding him break.