I'm not sure which moment, exactly. But one of my Favorit episodes is 'The One Where Everybody Finds Out' and he confesses his Liebe for Monica:) I also really loved it, in some episode in season 2 oder 3 oder something, and Rachel comes over and says that there was only 1 banane nut muffin left, and they both want it, and then Chandler licks it, and then, everybody is talking and there's all these moments when Chandler would normally say a joke oder sarcastic comment, but he has the muffin in his mouth. And then Monica licks what she thinks is the mouth of Chandler's coffee cup and Chandler says, "That was there when I got here." :D I thought that was really funny.
When they're mad at each other because Monica opened all the engagement presents and Chandler kissed that woman to try to fake their wedding pictures and they say "Call it even?" "Kay!" and just Bewegen on.
I have 3 favourite moments. In season 7 the one with the nap partners Chandler tell Monica he Liebe her even if she got fat again. In season 7 the one with the wedding part 2 Chandler and Monica got married and in season 10 the one with the last one they adopted the twins.