It might be a weird entry but the Jets' apparent disdain of Shrank and Krupke's racism towards the Sharks. Sure they're rival gangs, sure they're leading violent lives that can only end in tragedy, and sure they do honestly hate the Sharks... but they refuse to let it be about racism. For them, it's something else entirely.
Tony and Maria excitedly discuss how they would get married in the sewing shop, using mannequins to represent their parents and friends.
Likewise, both gangs briefly get together to mouth off to the cops. They even stick up for one another. Oddly enough, if the cops were around more often, the gangs probably would've cooled off eventually.
The fire escape scene. The whole scene is one long CMOH.