The time he stole his steering wheel (right out of his fucking hands while he was very much driving and trying to avoid being killed Steve it's not funny in hindsight).
Every single time Sam gets into the driver's seat of their car (a single vehicle provided by their benefactor, because apparently they come as a set now and Sam's not sure when he agreed to that) the Trauma Twins exchange a look, being extremely unsubtle about the fact they're only not commenting because Sam will actually murder them both, and he doesn't need that in his life. He's already stuck calling his mom on burner phones and trying to figure out what the fuck Wakandan food is (maybe the last place on Earth McDonald's hasn't hit, to be fair), he doesn't need running jokes from these assholes on top of that.
It's made worse by the fact he's the de facto driver for their little party, since Bucky's only got one arm now and Steve can't be trusted with anything bigger than a motorcycle ("Anything bigger than a tricycle, Sam. You didn't see him in the war, you think anyone ever taught this asshole to drive?" "'Scuse me for being too busy kicking Nazi ass to 'signal' my 'turns' or whatever." "I wish I'd never taught either of you finger quotes."). That means at least once a day he gets the 'I'm trying really hard not to make a Jesus take the wheel joke' look, and it gets old really fucking fast.
Bucky can kick the back of his seat all he wants, he's not riding shotgun. For some reason Sam finds him very distracting.
The time he ripped off Sam's wing and kicked him off a helicarrier.
The time he picked Sam up by his face and threw him across the room.
Yeah, okay. The kid was brainwashed both of those times. But that doesn't mean Sam's going to let being picked up by the face slide anytime soon. He doesn't bring it up, because Bucky gets that guilty look on his face whenever someone mentions something he did when he was out of his mind (which happens more often since they've been here, because it turns out there are endless triggers planted in his brain that he has no idea about). It eventually comes out when the Wakandan specialists are studying the security footage of the fight they've acquired to see if there are any clues to the trigger, and then there it is on the big screen: Sam getting picked up by the face and tossed aside like a ragdoll.
Bucky doesn't say anything at the time, studying his remaining hand like he's too ashamed to look anyone in the eye, but there's a wilted-looking sunflower and a card on Sam's bedside table when he gets back to the house that night. Which, y'know, former assassins creeping in his room isn't a huge invasion of privacy, or anything.
Sorry I used your face as a handle and tried to kill you and stuff is scrawled messily inside the card, which totally doesn't make Sam smile. He doesn't keep the sunflower until it's totally past dry and dead either. Definitely not.
The whole Wakanda thing.
Sam isn't exactly ungrateful to not be rotting away in some supermax penitentiary where the guards are definitely more racist than usual and the food is a punishment in itself. He's obviously happy to be able to walk outside every day and do whatever the hell he wants, within reason. But Wakanda is a lot, to put it bluntly. It's loud and busy in the capital city, and the crush of people and endless noise doesn't do Sam's PTSD any favours.
His life has changed dramatically since he started working with the Avengers, but he had his home routine worked out to manage his symptoms and things were pretty much as stable as usual. Now everything is new, different and potentially threatening, and it's not like Sam can call his therapist from the burner phone. But he's stuck here because of Bucky, because this is where he can get treatment (and Steve won't leave him and Sam sure as hell won't leave the two of them to get weird and co-dependent on their own because the world wouldn't survive), which he doesn't exactly resent but. It's not a picnic.
He doesn't realise anyone has noticed him struggling until Bucky leans over the table at the café they've stopped in to grab lunch before a meeting. They're trying to hash out some kind of deal with the Wakandan government, shelter for the fugitive Avengers in return for letting their enhancements be studied (without turning Wanda into a lab rat, that's the issue), and Sam is already twitchy after a long week of meetings in rooms with way too many windows and only one exit.
"Switch with me, put your back to the wall." Bucky gestures with his head, expressionless in that weird way he doesn't seem to do anything with his face unless he consciously thinks about it, and Sam doesn't bother questioning the instruction before he moves.
Bucky's not super steady on his feet since he lost the arm, still adjusting to the change in his balance, but he doesn't seem bothered about flopping heavily into the seat Sam's just vacated. It is better with his back to the wall, he'll admit, because the glass front of the café was making him antsier than he'd realised.
"Three exits: front, side, and through the kitchen. One guy at the counter is carrying, I make four pocket knives on the kids in the corner." Bucky rattles off quietly, placid as ever. Sam wonders if he ever does this to Steve, or just to himself for reassurance. "I'd head for the kitchen, I can do a lot with one arm and a knife."
"Counter." Sam nods, looking around to work out his own strategy. "Disarm the guy, take his gun, take cover. Then cover you and your bullshit knife plan."
Bucky smirks, right before opening his mouth to explain exactly why his knife plan isn't bullshit, and Sam realises he doesn't feel quite so anxious anymore. He's still not letting Bucky off the hook for getting them stuck in a foreign country, but he guesses at least the guy makes it easier to handle. Sometimes.
The fact he's a terrible fucking housemate.
Other times, Bucky makes precisely nothing easier to handle. Living with him being the biggest one. Sam knows he was on his own for two years, but as a housemate he's fucking ridiculous.
T'Challa arranged what's basically a mansion for them all to share, on the outskirts of the city where they're less likely to cause collateral damage if someone (someone who spends most of her time bitching about the wifi and trying to beat Clint at darts) goes nuclear. It's big enough for each of them to have their own room, plus enough bathrooms that there's a minimum of banging on doors and yelling about not using up all the hot water. It's basically luxury, and Sam should be finding it way easier than his college house share and five guys sharing one bathroom.
Except. Barnes is the housemate from hell and for some fucking reason they've ended up sharing a floor. He sets the new roll of toilet paper on top of the old one instead of actually changing it, he leaves one swallow of orange juice in the container and puts it back in the fridge, and he's this close to catching Sam's hands after he figures out who's going behind him and changing the thermostat back every single time he adjusts it. It drives Sam crazy, makes him finally understand why his mother hulked out about him not drinking from the carton as a teenager after he gets garlic backwash Barnes the fuck, and the final straw makes him sincerely wish he'd never volunteered to be Steve fucking Rogers' latest babysitter.
They're supposed to be leaving for the King's offices in five minutes, so Sam only bothers with a cursory knock before barging into Bucky's room because he must be ready by now. He doesn't expect to get an eyeful of pasty naked ass, bent over to let his hair hang down as he blow-dries it, and oblivious to being watched until Sam lets out an undignified squeak of surprise.
"Uh. I'll be there in ten." Bucky straightens up and looks over his shoulder, not even making an attempt to cover himself. Not that Sam's complaining, he's got a pretty nice ass for a white boy, but they're late and he doesn't need a boner right now and Bucky is the worst.
"Yeah, he's always been like that." Later on, waiting for a very tardy T'Challa to get to their meeting, Steve is less than sympathetic to Sam's traumatic experience. "Clothes aren't his strong point."
"How the fuck did you live with that asshole for years?"
"He sucks a good dick." Steve shrugs. Sam chokes on his water and Bucky smirks from the other side of the conference table like he knows exactly what they're talking about.
He hates them both. So much. He swaps rooms with Clint and definitely doesn't think about Bucky's ass ever again.
Going back into cryo.
It's not like Sam likes the guy, or anything. It's not like he's got used to having Bucky around, a solid and kind of weird presence that never really abates even after he's left the room. Having someone on his six has helped him adjust to being in a new country where he can't quite scope out the threats effectively on his own, sure, but it's not like Bucky's been doing that on purpose. And yeah, maybe they've started hanging out voluntarily sometimes, rather than being forced together by circumstance, but that doesn't mean anything when there are limited choices of people to hang out with in the first place.
But it has been nice to see Steve actually smile for the first time in two years. Even despite how difficult things have been, in the face of the panic attacks and tripped triggers and episodes of dementia that leave Sam understanding why Bucky had wanted to be left alone, Steve is happier than Sam's ever seen him when he's around Bucky. It's probably rubbing off on him, affection by proxy, because it's not like he could organically be happy to spend time with the guy who tried to murder them all. It's not like seeing Bucky grumpy and sleep-rumpled and drinking milk out of the fucking carton again makes Sam feel weirdly warm inside. It's not like hearing that Bucky's decided to go back under until they figure out how to deprogram him makes Sam's heart sink, makes him feel about as upset as Steve looks at the announcement, because he can't picture being without that weird, solid presence he's adjusted to having at his elbow.
It's not like Sam likes the guy, or anything, except the part where he totally does and managed to figure that out right before he's going to voluntarily put himself in a coma again. Sam fucking hates him.
He makes it to the lab just in time. Steve has stepped out to get some air (because he never lets Bucky see him cry, Sam gets the full joy of that all to himself), and Bucky's all alone sitting on the exam table and looking at the cryofreeze machine like it's going to bite him. Like this isn't something his dumb ass volunteered for, begged for so he could finally sleep. He looks up in surprise when the door slams open, face quickly twisting into something else when he gets a look at Sam's expression.
"I hate you." He storms over to the table, stopping right in front of Bucky's white scrub-clad knees and clenching and unclenching his fists because he doesn't know what to do with his hands. "You tried to kill me at least three times. You made my best friend into a zombie looking for you for two years. You make fun of my driving every time we get in the fucking car. You're late to everything and you make me late too. You're a terrible roommate, you never clean up your shit and you wake me up five times a night with your goddamn music."
"Sorry for the killing thing." Bucky is looking at him like he's insane, notably doesn't apologise for anything but the whole attempted murder business, and Sam wants to punch him.
He grabs the front of Bucky's stupid fucking scrubs and hauls him into a kiss, instead. Bucky makes a startled noise against his lips, but quickly gets with the program and rests his hand tentatively on Sam's waist, kissing back for all he's worth. It feels like way too little time before they pull apart, prompted by a beep from the cryo machine that breaks the spell between them.
"I hate you." Sam croaks, jaw set as he cups Bucky's face with one hand and tries to memorise how it feels. "You'd better wake up soon, you fucking asshole."
"Wilco." Bucky looks slightly stunned, and Sam can't blame him for that, but he doesn't look unhappy with the development. "Keep Steve out of trouble for me."
"I'm amazing, but I'm not a magician." Sam snorts, and Bucky kisses him again instead of telling him to keep himself out of trouble too.
Emotionally compromising him before fucking off into the freezer without even getting him laid. Sam's definitely not moving his seat when Bucky asks him. Ever.