Trendy or otherwise is fine.
I like “joke’s on you” when it doesn’t really apply, as in, “Joke’s on you, highway patrol, because I’m not speeding.”
I stick to the classics like “Pound Sand” or “FOAD” although there are a lot of times my grandaughter says, “That’s what she said”, that crack me up.
Right now I’m partial to saying “Look at that <thing>!” followed by “I work out!”
My kids hate it.
“_____ ALL the things!” It’s both a meme and a catchphrase, which originated on Hyperbole and a Half. The original was “Clean ALL the things!” It’s fun to say, just fill in the blank with any verb. It’s a meme lib!
“Sit on it!” from Happy Days. I guess I haven’t heard it enough for it to get old.
:smack: I just posted this in the other thread where it probably didn’t belong:
Son and friend came up with an idea to get rich, and his friend said, “We could make tens of dollars!” 
“Give your head a shake!”
Now morphed into " Give your head a wobble!"
I don’t use it myself, but I like “bring it.”
I like “Say whaaaat?!” as said by Stewie Griffin.
“If you can’t do the time, don’t do the crime.”
My new favorite is “I heard that about you”, a variation on “that’s what she said!”
I especially like to use it when it makes no sense whatsoever.
Wow, I use that all the time. I didnt even know others did.
Others I use
FUBAR - fucked up beyond all recognition
PDU - poor dumb user
Im laughing at you, not with you (for some reason, this one pisses people off)
When people start any statement with “I think”, I will respond with, "I disagree with the first two words of your statement’. Most are confused when I say that too, ironic.
Out of the gene pool please…
About forty years ago, I watched a teleplay version of Kurt Vonnegut’s stories: Between Time and Timbuktu. I also had the book in script form, and toward the end, astronaut/poet Stony Stevenson is in NYC, and meets up with a bum. Stony tells the guy about his adventures in time and space, and the bum says, “That’s the saddest story I ever heard.”
So sometimes, when someone tells me about their day, I’ll say, “That’s the saddest story I ever heard,” just to screw with them.
Other times I’ll say, “Yes? And?” or “So what can we learn from that?” when they’ve finished their stories.
SOCMOB.
Standing on corner, minding own business. It’s what my patients were always doing just before they got beaten/shot/stabbed by “these guys” etc.
I bet that goes over really well at your workplace 
And who said doctors don’t have a sense of humor and good bedside manner?
I’m half trying to keep the “let’s go down to the quarry and throw shit in there” one alive a but a certain poster here aint paying me enough.
Any time anyone asks me any question… “so it’s come to this.”
After someone’s related a humorous anecdote, a beat after the punchline… “and then what happened?”
“Are we having fun yet?”. From Zippy the Pinhead.
“Meanwhile, back at the ranch…”, when someone or something is taking its sweet time. Also, “Whenever the spirit moves you!”
“My name is wartz?”, from Being John Malkovich.
Always loved the perfect imagery of “barking up the wrong tree”.
Note the thread title. I love hearing that one. I don’t think I’ve ever said it to a patient. But I’ve heard my patients say it hundreds of times by now.
“So that’s what the kids are calling it these days.”
“If you know what you’re doing, it’s not an adventure.”
“Guess I picked a bad week to quit drinking.”
Butthurt. Even better: Butthurtedness