There are guys who take blowjobs like it's their God-given right to have somebody on their knees, and then there are guys like Jack O'Neill. There's a lot of space in between, but John doesn't mind where Jack is on the spectrum. Gratitude tastes good on anybody, even a general, even the guy who pushed John into taking this Hail Mary of a mission.
He pulls back and licks his lips, glancing up at Jack. Jack's still got his expression closed down, but his body can't lie, not to someone who's given as much head as John Sheppard has over the years. This has to be the first time he's fucked somebody's mouth in ages. John's going to be smug later, when he jerks off thinking about this.
It could be the last time for him for a while, too; he doesn't know how tight a ship Sumner runs, but he has a feeling Sumner's not one of those commanders who turns a blind eye to who's fucking whom. But he's not going to think about it right now; Jack O'Neill is fucking into his mouth like it's the best thing he's felt in who-the-hell-knows how long, and John doesn't want to miss a minute of it.
Jack's cock is thick, a little too long for this to be comfortable, but that's good--John doesn't want his last blowjob on Earth to be comfortable. He wants it rough, tough, and almost mean; he wants Jack to get his hands into John's hair and drag his mouth down until John chokes. John shoves forward hard, again, again, and when he gags a little and shoves right past it, Jack gasps and puts one hand in John's hair--almost tentative.
If it wouldn't get John's ass kicked, he'd say it was cute. It's hard to be a smartass when your mouth's full of dick, though, and so John gets right back to work, pushing past his gag reflex again and burying his nose in Jack's pubes. This time Jack's hand clamps down hard against the back of John's head, and he thrusts forward a fraction of an inch. John takes it, and when Jack gets his other hand up and slowly, slowly drags John's head back, John steadies himself and spreads his legs a little wider. This is it.
He puts his hands behind his back, laces his fingers together. He lets Jack drive, but he's ready now, and when Jack's cock shoves into his throat he doesn't choke this time. He just takes it, makes himself open as wide as he can, loses himself in the taste and smell of sucking cock like this, like there's nothing to him but his body, and of that, there's not much but his mouth, his throat, the way his lips work against Jack's skin. Jack's cock sliding over his tongue, Jack's voice up above him panting out curses, Jack gripping John's hair hard and the pain going right to John's cock.
It's all absolutely fucking perfect, and when Jack slams in one last time and comes, John does choke, body jerking, hands tightening on each other. Jack backs off fast, so fast he's still got one shot left in him, and it jets across John's chin and leaves him sticky.
"Greedy," Jack pants, "fucking," another breath, "bastard," and he sinks down against the wall and lands with an oof, leaning forward so he can lick the come off John's chin. John whimpers; he's so close and that's so damn dirty and he just needs, just wants--he backs off a step and puts his knees around one of Jack's legs, rubbing up, cock sliding against Jack's shin. Jack's eyebrows go up, and he says "Oh," and just like that he's on his knees, too, with one hand in John's pants, working his cock nice and easy while he finishes licking John's face clean. He kisses John once the come's gone, and John opens his mouth and lets Jack slide his tongue in, lets Jack fuck his mouth this way, too.
Jack twists just under the head of John's cock, and John grunts and comes; Jack slides a come-slick palm down the length of his cock and gives him another squeeze, which makes John groan again. He rests his head against Jack's shoulder when it's over, and Jack pats him awkwardly on the back.
"You okay now?" Jack asks softly, a little later, when he's got John up on his hotel bed. He doesn't get much of a response out of John, just an ear-to-ear grin. He lets himself out, and John flicks the bedside light off. He's got a feeling this is going to be the best night's sleep for him for a while, so he's going to take it for all it's worth.