Steve Rogers & Tony Stark:

Tony reminds Steve of a secret weapon he gave to him and that only Steve knows about. And Steve...

...uses it to great effect.

In the story Relics from Captain America V. 3 #50 Steve bounces the shield around his flat while he’s on the phone with Sharon and we get to see a present he received from Iron Man. 

Presenting what they know in the White Hose like a well oiled machine - finishing each other’s sentences and understanding each other well.

Steve: I don't mean to make things difficult. Tony: I know, because you're a very polite person. Steve: If I see a situation pointed south... I can't ignore it. Sometimes I wish I could. Tony: No, you don't. Steve: No, I don't. Sometimes... Tony: Sometimes I wanna punch you in your perfect teeth. But I don't wanna see you gone. We need you, Cap.

“No matter what. I promise you, if you need us, if you need me, I'll be there.”

Steve: I will miss you, Tony. Tony: Yeah?

Steve tells Tony he’ll miss him and Tony sounds like he absolutely wants to beleive him.

Tony: How were you guys planning on beating that? Steve: Together. Tony: We'll lose. Steve: Then we'll do that together, too.

-

Tony: Well, like the old man said. Together.

Learning to be on the same page at last. 

“Play nice, Tony.”

In an argument with Protector, Tony calls on Steve to back him up.

Tony: I don't trust a guy without a dark side. Call me old-fashioned. Steve: Well, let's just say you haven't seen it yet.

Tension rises. Steve shows off - and Tony? You’re totally staring.

Tony: Uh, actually, he's the boss. I just pay for everything, and design everything and make everyone look cooler.