1. Ship's Counselor (Jim prefers the term Love Doctor, though he'll only admit to that one when he's drunk)
They come to him for advice on so many things he's not equipped to handle. Chekov most of all because he's so damned young and the way he looks at Jim is kinda scary. All starry eyed and one step away from indecent. Still, the kid comes to him for advice (and how fucked up is that? A 17 year old boy coming to Jim, who's only 26 himself, asking for advice on, of all things, relationships). Jim's not exactly good at relationships himself, he's always been more fond of the friends-with-benefits plan or one-nighters in general. On top of that, he's still a bit uneasy about the way Chekov looks at him.
Thankfully it's a passing phase. Not the hero worship or the asking for advice, but the hungry looks. Well, they're not gone, but Jim's happy to see them swing from him to Sulu and he's glad that the two young men are getting along as well as they are and even more so, he can see that Sulu's more than a little interested in Chekov as well. It also explains in the beginning, how Sulu would sometimes have some pretty odd mood swings around Jim. Sometimes he'd be all friendly - hey, Jim'd saved his life, right? At other times, and often after Chekov had spoken with Jim, Sulu would be giving him some pretty dark looks.
Figures, of course, that Sulu has a jealous streak a mile wide.
However, now Chekov just comes to ask for advice on stuff Jim would really rather not be asked about. He wonders if this is how it is to be a father? Some of Chekov's questions can make even him blush. Thankfully, again, when Chekov finally does end up in a relationship with Sulu, they seem to figure those things out on their own.
Unfortunately, now they both come to him when they've had an argument. Not together, no, but each on their own time.
Jim's pretty sure he didn't sign up as ship's counselor.
2. Girlfriend. (He's all of the sudden Uhura's girlfriend. No seriously!)
It all starts about a month into their first five-year mission. She comes to him one evening, after shift and asks if she can have a word with him. Turns out she has had little time to talk to anyone about what had happened at the destruction of Vulcan. They've both lost friends and acquaintances at Nero's hands. Most of all, though, they start out talking about Gaila, swapping memories and slowly getting to know each other. Jim's long since put his attraction to her aside. Not that she's not still absolutely stunning, but within this short span of time, they've seen each other nearly broken, beaten and at their worst and quite frankly, Jim already knows that he wants no one else as his Communications Officer. No doubt about it - he doesn't want to fuck up the friendship he has with her, nor ruin their working relationship either.
So they talk, and he'll hit Bones if he ever infers that they paint each other's toe nails again. That was just the one time and they'd both been shitfaced and in need of a good laugh. Besides, the silvery sheen of the polish was kinda sexy. Even Uhura had said that, between gasps of laughter and tears.
3. Being put to work in Engineering (aka a nifty way of hiding)
Jim's liked his crazy Scotsman since he met him. The man defies labels, and Jim likes that. Also, the man can create miracles with a roll of string, a phaser and a rock.
So it starts with Jim occasionally... erm, hiding in Engineering, because some days it all just becomes too much. He's too young, he's too inexperienced and although he suspects Spock intercepts a lot of shit that's normally a captain's job, there are times when he wants to find a dark corner and curl up in there, hiding.
Turns out Scotty seems to think anyone in Engineering is fair game and can be put to work. Especially Jim, when Scotty figures out just how stupid Jim's not. Secretly, Jim likes that. When other people relax with a holovid or some such, he actually likes to fiddle with equations and between him and Scotty, they come up with theories that would make most other people run away screaming. Well, maybe not Spock, but the one time Spock found them, in Engineering, sharing a bottle of whiskey, their weird and wild theories warranted a full lift of the eyebrow.
Jim considers that Spock's equivalent of running away screaming.
4. Being Starfleet's version of a hot piece of ass
It's so not in his contract that he has to shake his ass at official functions to lure potential allies into the fold.
He's especially not too hot on the idea of shaking anything at the Klingon officials. Never mind that Kohr is totally hot for him, especially when Jim says yes to spar with him. In the name of friendship, of course. Jim is absolutely sure that Kohr cops a feel more than once. Although it can be hard to tell the difference, because the sparring round leaves him with so many bruises and there's a huge difference in how hard 'copping a feel' is when it's done by a human and when it's done by a Klingon.
Also, Jim can totally live without knowing what a leering Klingon looks like. But hey, they came out of it with a signed truce. Even Jim can't argue against that.
5. Ingesting weird substances/pollen etc for the sake of science - just so Bones can jam those damned hypos into his neck.
Jim has a theory that if he checks the percentage of missions where they end up ingesting/inhaling weird substances and or pollen, the numbers will be a lot higher than found on any other Starfleet vessel.
It's his luck that his Vulcan first officer, because of his unique physiology, is either immune or at least, can resist it for longer than the rest of the crew. Spock's saved their uninhibited asses more than once. Although there's been once or twice where Spock's succumbed as well, and although Jim has only vague memories of those times, what he does remember will never ever make it into his reports for Starfleet. A cuddly Vulcan male is not only a little scary, but also fucking adorable. Not that he's ever telling Spock that. If he did, Spock wouldn't believe it, even though Jim is 99% sure that Bones is hiding a stash of pictures taking from that day, saving them for a day where he'll need some leverage with Spock.
Jim's both looking forward to that day with excitement and fear. Spock's a force of nature. Granted, a very quiet one, but no less dangerous.
So yeah, Jim might not have signed up for any of that stuff, but then again, he could be wrong, there are a ton of foot notes in the rules and regulations of Starfleet.
+1 Submitting himself to weird alien mating habits (and leaving his days as an intergalactic playboy behind him)
Used to be, Jim rarely said no to a sexual encounter, be it male/female/non-specific gender on offer, and he's lying if he claims he didn't like it that way.
It also used to drive Bones completely insane, because it meant more checkups of Jim than should theoretically be necessary, especially considering he's the Captain. Never mind what he'd needed of help from Bones when he'd still been a cadet. Sometimes Jim's pretty sure that Bones enjoys injecting him with shit, just for the hell of it.
Bones should be happy that those days are over, but now he just gives Jim this pained look whenever Jim brings other sexually related problems to him.
See, it's all because his first officer is so damned weird, but Jim's still completely head over heels in love with him. And Spock's terribly possessive, which is why Jim doesn't sleep around. Well, even if he does occasionally window shop, he's not really tempted. Who the hell would trade having Spock in their bed at night for anything else?
Once Pon Farr hits (and Jim's beginning to understand that Vulcans have a lot of secrets, a lot of them regarding sex and emotions) there's no going back for him. They're connected in both mind and body now and Jim knows what lurks underneath that perfectly controlled surface.
He knows that it baffles Spock that he doesn't just accept it, but welcomes it. Jim figures Spock might never understand that particular little thing about him and that suits him just fine. It helps to keep Spock on his toes and their relationship from ever going stale.
Also, the sex is really, really amazing and although Jim knows he didn't sign up for any of it, the sex, the relationship, the bond and cohabitation? He wouldn't change it for anything in the Universe.