Armand's I Am What I Am speech to Val. Even though he ends up subverting his own self-assertion, it's only because he wants his son to be happy.
Armand: Yes, I wear foundation. Yes, I live with a man. Yes, I'm a middle-aged fag. But I know who I am, Val. It took me 20 years to get here, and I'm not going to let some idiot senator destroy that. Fuck the senator. I don't give a damn what he thinks.
After the woman who gave birth to Val accidentally shows up and introduces herself, Val drops the entire act and reveals that Albert is his real mother.
Sen. Keeley: How many "mothers" does Val have?
Val: ...Just one. [removes Albert's wig] This is my mother. My father owns the club downstairs, my mother is the star.
Sen. Keeley: What?
Val: We lied to you, Barbara and I. And everyone lied for us. These are my parents.
Armand: [indicating Albert] This is my wife. [indicating Katherine] This is the lady who had Val.
Val: Nice to meet you, Katherine.
Katherine: [fondly] Very nice, Val. [to Albert and Armand] You've done a good job.
Even though Katherine and Val have never properly spoken, she doesn't hesitate to help when Armand asks ("Cancel my appointments"). When she briefly gets to speak with Val on the phone before arriving, she's clearly overcome with emotion, but states nonetheless she's happy to finally help her son. Such small moments but Christine Baranski nailed it.
Armand's speech to Albert at the bus stop:
Armand: My cemetery's in Key Biscayne. It's one of the prettiest in the world. The sky is blue, palm trees, rolling hills. The one is Los Copa's really shit. [sighs] What a pain in the ass you are. And it's true: you're not young, you're not new, and you do make people laugh. And me? I'm still with you because you make me laugh. So you know what I got to do? I got to sell my plot in Key Biscayne so I can get one next to you in that shithole Los Copa, so I never miss a laugh.
Armand: I'm 50 years old, there's only one place in the world that I call home and it's because you're there.
That small moment where the sit quietly holding hands after Armand gives Albert the palimony agreement.
Although Katherine is maternally distant from Val, she genuinely happy at the prospect of connecting with him and doing a favor for him.
Val's thoughts on being raised by gay parents? "I'm the only guy in my fraternity who doesn't come from a broken home."
Doubling as a Tear Jerker, Barbara's small, quiet "I would have really liked to have had you as my family" to Armand and Albert as her parents try to drag her away.
While it's a first and foremost a joke, the scene of Armond getting in the face of the guy who is understandably annoyed with Albert bumps into him shows how quick he is to defend his beloved partner. Up to and including a fist to the eye.