1. Tony Stark.
It wasn't the first time Sam had met Tony Stark, although he doubted Stark remembered him specifically. Stark certainly remembered the technology, and was quick to offer his services in repair and/or rebuilding, but the pilot himself was only barely more significant now than he'd been back then.
His impression of Stark at the time was of insufferable arrogance and callous disregard for common decency. In retrospect, he can see the form of a completely unconscious emotional shield, although the realisation doesn't make the memories less irritating.
Stark obviously rubs Steve the wrong way, but rather than getting riled up, Steve just fixes Stark with a "Seriously?" eyebrow and ignores him.
"Anytime you want to get out of here, just say the word," Steve told him, after one such encounter.
The present Stark uses his arrogance as a way to put people off guard - he wants to be underestimated. That, coupled with some lingering PTSD issues, makes him alarmingly easy for Sam to understand.
"It's fine," said Sam. "He actually wants us here. Can't say that for anyone else I know."
2. Bruce Banner.
Since Stark got distracted by an urgent call from his delightful CEO, Natasha ended up leading the tour of the building.
"This is Dr Bruce Banner," said Natasha. "He's Stark's pet scientist."
"Natasha," said Steve in warning, although it was at least partially feigned because he was obviously biting back laughter.
Banner laughed nervously. "No, that's accurate. I keep expecting him to get bored and let me go. He hasn't made any indications that he wants me gone, so I stick around."
"I am pretty certain Tony Stark would not be afraid of just telling you to leave if he wanted you gone," Sam pointed out.
Banner just looked at him with serious eyes, and said, "You would be surprised how many people are afraid to ask me to leave."
It was a few days before he realized the significance of that statement.
3. Natasha Romanov
Natasha comes and goes, usually without warning. They hadn't even realised she'd be at Stark Tower when they landed on its doorstep, although it wasn't hard to see how she'd reached the same conclusion they had.
In the Tower, she's soft and relaxed, teasing Steve about girls and meeting every one of Stark's remarks with a tart rejoinder.
She doesn't talk about what she's doing outside the Tower, and Sam doesn't ask. But it's sometimes possible to see the delicate touches of her presence when he scans the world news headlines.
It's not the kind of war he'd like to fight.
A collection of articles is building up on the kitchen cork board, all bearing headlines along the lines of "The Real Natasha Romanov". They all carry wildly different stories.
Sam doesn't blame the journalists, though, because he strongly suspects Natasha doesn't know either.
4. Clint Barton
Clint Barton arrives at the tower beaten and bloodied, bearing a battered bow and a dog.
For the first week, Clint hangs out on their couch, feeding the dog pizza and being generally sarcastic. He goes loose around Natasha, loses some of the tension he carries in his shoulders and makes jokes that are less pointed, more affectionate.
His "I don't want to talk about it" is a lot less believable than Natasha's, but Sam doesn't press the point.
He knows how to deal with the Clint Bartons of the world. He'll open up eventually, once they have a few beers together and Clint lets him in.
5. Steve Rogers
It's much easier to spot Natasha in the news than the Winter Soldier. Sam comes back from following another lead to another dead end, and Steve doesn't even say a word.
"We'll find him," says Sam.
"I know," says Steve, and he doesn't say anything else.
Sam knows he should at least try to get Steve to consider what might happen if they don't find him; if the Winter Soldier went back to what was left of HYDRA without a second thought; if someone else found him first and took him out of the picture.
But, hell, blind confidence in the goodness of humanity already saved them once.
"Yeah. We'll find him," Sam says again, but he believes it more.
...And one time he did.
Sam always leave a card behind him when he follows a lead on the Winter Soldier. They have a phone number and the words "Call if you want to talk".
He likes taking the calls. They come from homeless addicts, dog-walkers, lonely seniors, anyone who might come across the card and need an attentive ear.
The time he hears nothing but heavy breathing for a solid minute, he stays on the line until the voice starts, rough with disuse.