I broke my hand playing frisbee, diving to make a catch.
Thanks. I’m glad you enjoyed it.
In all seriousness, one technique I found useful when I was primary care giver for my housemate’s baby was to imagine the way her cries would doppler if I were to duct tape her into a cocoon, hang her upsides down in the attic from one of the rafters, and start her swinging.
For me, the silliness of hearing the WAAAAAaaaaaaaaaaAAAAAAAAAAaaaaaaaaAAAAAAAAaaaaaa, even if only in my imagination, was enough to keep me from losing my cool with The Monster.
This is sort of off topic, but I was on the bus today and two freshman girls in front of me were discussing some guy:
Girl 1: “Did you hear he broke his hand playing basketball?”
Girl 2: “How embarrassing - too bad he didn’t break it doing something cool.”
I thought, ouch - what’s wrong with basketball? So apparently sports are not considered a ‘cool’ excuse.
Could be worse. For mandatory PT, me and a few Air Force buddies decided to do “a sport” but the sport we chose had to be on the approved list (don’t get me started). And of course the b-ball courts at the base gym were taken, and the volleyball courts… and the squash courts… so my buddy broke his pinky playing kickball.
When confronted by his coworkers, he started with “Oh, I dinged it up at PT.” If pressed, he would move onto “Oh, we were just playing ball, it was a lousy catch.” And if pressed even further, he would say “I BROKE MY PINKY PLAYING KICKBALL! IT’S FUNNY BECAUSE I’M WEARING CAMOUFLAGE AND AM SUPPOSED TO BE A FIERCE WARRIOR!”
Karma’s a bitch!
Karma Sutra and too much lubricant.
Just say “mini-golf”, and let them do the math.
If you try to pass it off as any kind of sporting injury, there’s a chance the person you say it to will be interested in that sport, and you’ll end up having to bluff your way through an awkward conversation.
If the purpose is to deflect further inquiry, the story should be as mundane and boring as possible. ‘I tripped on a rug’ or ‘got it caught in a door’ or something.
Treehouse.
Punching babies in prams outside Mothercare and some stupid c**t was using it to carry shopping with a lot of tinned goods.
Nah, they’ll probably want more info. I slipped and fell on ice in my driveway and broke my wrist, and people still asked - mind you these were people experiencing the same icy sidewalks that I was, so that should be a mundane thing. “Slipped outside.” “Oh, here at work?” “No, in my driveway.” “Was it icy?” " 
Yes." “Oh, you should be careful, it’s awful out, blah blah…”
I had one wisecracker who told me, “The last time I saw a cast like that on a woman, it was my wife after she hit me too hard.” (He then rubbed his head like she broke it across his skull, not like he retaliated.) I replied with, “Nothing that fun, no, just slipped outside.”
This wins it for me. 
You’re probably right.
How about looking frightened and urinating in your clothes? - that usually kills the conversation, I find.
With a pained and nervous look in his eyes ‘my wife told me to say I fell down the stairs’.
Or “It wasn’t like that! I can explain everything…”
Jack Bauer called him up to go kick Chuck Norris’ ass?
Barista, you say? How about a dead stare and the mumbled phrase “poor tipper”?
Sailboat
Act like it’s not there.
Think The Black Knight from MP and the Holy Grail. (‘I’ve had worse.’)
Friend of mine came to me -specifically- with the ‘broke my hand, need a good story’ request about a year ago. I was, honestly, flattered that I’d been approached as an ‘expert’ in the ‘entertaining BS’ department. As the guy is a notorious ‘dirty old man in training’, he’d originally gone with the ‘lost a masturbation contest’ idea. I told him in no uncertain terms that, really, if you’re going to lie about something like that, at least win the damn contest! 
My co-worker broke a thumb while riding a mechanical bull, so you could always use that.
He broke it on the final tryouts for American Gladiator when he had a huge lead and was sure to make the show.