Rating: K+ for mild language, some violence.

A/N: It's a miracle that John has never snapped after listening to Sherlock insult him for a while... Note that I know absolutely nothing about boxing. Bonus points if you catch the cannon reference.

Disclaimer:Sherlock belongs to the inestimable Moffat and the BBC and other people who aren't me. As always, a tip of the hat to ACD.

The worst time, it was because Sherlock was bored.

"Bored," came the moan from the couch. The twentieth such declaration in the last hour. One groan every five minutes. John was losing his mind.

"Shut up Sherlock, I'm not your personal entertainment system. Clean up the kitchen or something, heaven knows it needs it."

"Dull."

"You cannot be serious, Sherlock," John said, slamming his laptop shut. "Clean it, and clean it now, and stop whining about it. I swear, you act like you're four years old some days! I'm not your mother!"

"I'm fully aware that you are neither female nor related to me, John."

"Right. I'm off to the gym, it better be clean by the time I get back."

"Gym?"

"Yes, Sherlock, that place where blokes go to lift weights and get buff? Not everyone can stay in perfect fitness on a diet of nicotine and coffee and no sleep, we have to eat right and exercise regularly and rest occasionally."

"Can I come?"

"Absolutely not."

"So help me, if you pull one of your stunts, I will put laxatives in your coffee tomorrow, Sherlock."

"I promised I'd be on my best behavior, John."

"Why doesn't that make me feel better? Anyway, what would you like to try? Weights, ropes, the elliptical machine…"

"Boxing."

"Huh?"

"I've been meaning to show you a few techniques for a while. You do have a rather nasty habit of being kidnapped, I thought we might want to avoid that in the future."

"The only reason I get kidnapped, Sherlock, is because of you, and I assure you that I never make it easy for them."

"Put these on," Sherlock replied, tossing him some gloves.

John just glared.

"A little practice never hurt… ooof!" Sherlock grunted as John punched him in the stomach.

"I'd say that hurt."

Not surprisingly, the sparring lesson soon turned into an all-out war. Sherlock's advantage was his height and quick wit, while John's was his compact build, dry sarcasm, and wealth of ammunition.

"Please, John, that last punch was so predictable my dead grandmother could have seen it coming. Can your funny little brain come up with nothing better?"

"My 'funny little brain', Sherlock? That's rich, coming from a man who can identify two hundred and forty three types of tobacco ash, of all things, but can't be bothered to remember that the earth goes round the sun!"

"You 'can't be bothered' to update your wardrobe! Seriously, John, where did you find those ridiculously horrid jumpers? A fashion magazine from 1895?"

"So says the man who could pass as a woman's fashion model. Seriously, Sherlock, with your girlish figure and flowing locks, have you ever considered a career in crossdressing when your 'consulting detective' job falls through?"

"At least I have a job, Mr. Unemployed. I didn't need to flatshare, you did. I might despise Mycroft, but at least my sibling cares enough to not leave me in the lurch!"

"Your sibling? Besides being more of a prig than yourself, something that I wouldn't have thought possible, he's goddamn Big Brother from 1984! If I'm so dull, as you like to put it, why bother keeping 24-7 surveillance on me? I'm not blind, don't think I haven't noticed the tails. And by the way you're always on my laptop, I'd swear he was paying you to spy on me!"

"Dull, hardly covers it, John. Try insipidly, tediously, predictably boring. You give 'normal' a bad name, you're so unoriginally bland. What on earth would you do without me? Go limping back to that standard-issue, cookie-cutter, generic, nauseatingly average existence?"

"Without you? Without you, I wouldn't have to be worried about being poisoned in my own kitchen because of some bloody experiment you failed to warn me about. I would be able to open the fridge without wondering what random body part will be housed next to the milk, which you never buy anyway. And I wouldn't have to worry about being kidnapped every other month and beaten senseless over something I really don't know anything about, because someone didn't think it important enough to tell me. I wouldn't have to worry about being arrested for things I didn't do, or having to apologize to god and everyone about stuff you did, Sherlock. Every time I get into trouble, Sherlock, it's your fault!"

"My fault! You're the one that was stupid enough to be captured and held hostage like a pretty little princess. Next time, do swirl your skirts and swoon in order to complete the effect."

"I'm the princess? I'm not the one with a ruddy palace in their head. Is it pink and purple with rainbow trim? It would suit you, really. And if anyone here is a knight in shining armor, it would be me, the only military-trained, heavily-decorated captain in the room, who has actually saved a few damsels in distress in the real world, thank you very much, not in my imagination."

"Is that so? Well, then, where are all these grateful damsels now? From what I've observed, you must have a whole harem of rejected conquests. I swear, John, you go through women like Donovan goes through pantyhose."

"The reason I can't keep a steady girlfriend is because of YOU! And I am not collecting a 'harem of rejected conquests', because I, unlike a certain ridiculously dramatic someone, am a gentleman. I, unlike you, am capable of having a nice night out without horrifying, mortifying, embarrassing, and verbally eviscerating everyone in the room!" John yelled, punctuating each word with a blow.

"Everyone deserves it because everyone is an idiot, John, including you. I'm doing your poor little placid minds a favor by reducing the stupidity in the room and raising the IQ of the entire population," Sherlock retorted, rolling his eyes.

"I'm the idiot? I'm not the one that has to be reminded to eat every day. Or to sleep at least once a week. I'm don't make a habit of running off, unarmed, after dangerous criminals with no backup and no plan. All you see is the precious case. London could burn to the ground before you could be bothered to care about anyone, you machine!"

"Machine, am I? Fine. At least I'm not some sobbing sentimental useless friendless cripple…"

John saw red.

He'd been able to keep his head throughout the fight, he'd had a lot of practice bearing Sherlock's insults. But never before had Sherlock purposely aimed his razor-sharp tongue to wound John. Whoever said words could never hurt them had obviously never been in an argument with someone they cared about. Getting the crap beaten out of him definitely hurt less. Hell, getting shot was almost preferable to hearing the words 'useless friendless cripple' come out of Sherlock's mouth.

"John." His name wavered up from the floor. Apparently John had knocked Sherlock down (out?) in his furious barrage of wrath.

"John, I'm sorry."

Any other day, he would have been surprised. He would have been excited, even proud that the Great Sherlock Holmes had decided, for once, that he was not perfect, that he was wrong. Not today.

"John, I didn't mean it." Yes you did. John threw down his gloves and stalked out of the room.

"John…" Sherlock trailed off miserably.

A/N: This story doesn't end here! Due to popular demand, I expanded it (extensively) into "Hard Knocks". Check it out!