I love slang. I particularly like the old stuff people don’t use anymore.
“Everything’s Jake!”
“He fell on his keester.”
“I’ll kick ya in the slats!”
“Pour me a cuppa Joe.”
Got any more?
I regularly use “aw, nerts!” and “ba-nanner oil!”
You guys are the cat’s meow, by cracky!
I forgot about the Cat’s Pajamas and the Bee’s Knees!
By cracky. Heh.
Sca-rew
Haj
I love “boffo.”
I use it at least once or twice a week. I like to imagine all those youngters scurrying off to find a dictionary. (In reality, they probably skip right over it, muttering “nutsy old fart and his goofball old words that nobody remembers.”)
I’ve been calling people “puds” lately. My kid got me started on that one again. Heh. Ya pud.
Yee Gods! I’ll be over yonder if you need me.
My hubby and I say cat a lot. As in ‘Get a load of that cat!’ or ‘What’s that cat’s problem?’.
We’re not talking about felines, either.
Oh, my stars 'n little hoppy toads!
Waall, I swan, that’s a humdinger!
Pour me something to cut the phlem.
(fast driver) He was modockin’.
Quit nammyjackin’ around and do something.
You young whippersnapper, I oughta tan your hide.
He’s too big for his britches.
She’s got moxie, I’ll give her that. (nerve)
(after a bad hand of cards) I didn’t even get a smell.
She’s still wet behind the ears.
Everythang is everythang.
We drove 'round Robin Hood’s barn, and we finally found it a stone’s throw from where we started.
It’ll take me a month of Sundays to get all that fixed.
He gave him a klop in the kloop. (blow to the head)
Isn’t it a tad early to claim that
‘You young whippersnapper: I oughta tan your hide: He’s too big for his britches: She’s still wet behind the ears: and the Bee’s Knees!’ are old slang needing revival? They never stopped being used by the people I know.
Dinglewhompas - I just love that word.
Skylarking - another good classic.
do what?! be’ave! you all think you’re 'ard do ya? with ya “Dinglewhompas” and “cats”?
well don’t you adam an’ eve it! i mean, jesus h, you’re avin’ a bubble ain’t ya?! you’re a buncha big girls blouses - shut ya cake 'oles the lotta ya!
I’m in London me old chinas - its the dogs when it comes to slang innit!
BRING IT ON 
Take it on the heel and toe.
Keister
Keister-stash it (rude)
Maybe they’re current where you come from, brother Bippy, but they were quaint when I was a kid. I’m 53 now. Nobody I know says “whippersnapper” without putting on a Grampa Simpson-like voice. 
My dad has some classics like, “Go piss up a rope” or “go shit in your hat!” I also like to use words that were in when I was a kid, like “rad” and “gnarly,” which are no longer used. Also, “groovy” has a vintage feel to it these days, though Austin Powers has helped keep such words alive.
I used “when Hector was a pup” and “queer as old Dad’s hatband” a few times and NO ONE knew what the hell I meant, so those must be out of date.
My old boss had a good one … “when God was a corporal.”
“brazen hussy”: My college buddies and I would jokingly call each other that.
I also like “living in sin.” Makes it sounds ever so much more exciting.
I use “hepcat” a lot, but mostly for sarcastic purposes, poking fun of someone who thinks he’s cool or hip. I once called a nemesis at work “a slicked-up hep daddy”, it had the proper ego deflating effect. He didn’t expect something like that so much younger than him.
I call people “Daddy-o” way too much for my own good.
“Don’t know him from Adam’s housecat,” and variations.
I still say “in like Flynn” rather than “in like Flint”, although even those Derrick Flint movies were mostly forgotten until Austin Powers came along.
I refer to myself and others as “squares.”
I use “rough row to hoe”, because I’ve done it.
“Shuck and jive.”