He’s got a hitch in his giddy-up. (He’s tired, sick or injured)
How’s your mommer an them? (How’s your family doing?)
He done got all bowed up. (He became defensive/angry)
That’s slicker’n goose dookey! (That’s very clever)
Well I see Cooter Brown made the rounds from Texas to Georgia 
“Bigger 'n Dallas”
“I’m gonna stomp a mudhole in yore ass”
And “suckin’ hind tit” was when things were going the opposite of great.
I have a quart paint can (clean, empty) sitting on my file cabinet with a homemade label: “VunderBob’s Big Ol’ Can of Whup Ass”. It’s one of my favorite office toys.
Ah, but if he was doing really well, he would say, “Finer 'n frog hair…split three ways!” 
My personal favorite is “I’d rather sandpaper a bobcat’s ass in a phone booth”
“Ah’m gonna build a shoe store in yore ass, an’ then ah’m gonna stomp out a cigar on the carpet.”
love your location 
You ain’t gonna walk it dry?
I use “rode hard and put up wet” to describe anything that’s kinda rough-lookin’.
“Might could” and “fixin’ to” are real words.
In the South, “We’s fixin’ to go, but we might could stay” is a valid sentence.
This may not be a “Southern-ism,” but it sure sounds like one to me:
“No sense in puttin’ Cool Whip on cow shit.”
(Said to me by my dad whenever I requested a new shirt, shoes, or anything else he didn’t think I needed.)
Not from the south but one of the best I’ve heard in a while…
(while discussing a woman observed the day before)
“She was so good lookin’ I had to go home and f*ck my wife.”
My Kentucky grandfather and father had a few:
“Lower than a snake’s belly in a wagon rut.”
“Busier than a one-armed paper hanger.”
“Running like a striped-a$$ ape.” (very very busy)
“It’s better than a burnt stick in the eye.” (Seems like this should be an Odyssey reference, but my grandfather’s never read it).
Dad also says the one about the bobcat’s butt in a phone booth.
“Turn it loose”=let it go
“Leave go of it” = let go of it
“Don’t you do me that way” = don’t behave that way to me
“It’s raining pitchforks and hammer handles.” this may actually be a Midwesternism, I don’t know.
Ahh… and we use the “finer than frog fur” too.
Mrs. Furthur
Texas variant popularized by former NFL Monday Night Football announcer Don Meredith and TV character Hank Hill: “He’s got a hitch in his get-along.”
One of my favorites- I usually say “I’d rather wirebrush a wildcat’s balls in a phone booth” then (perform some task)
I said it once to my boss and I think he hurt himself laughing.
He’s busier ‘n’ a one-legged man in an ass-kickin’ contest!
“Hog wild and pig crazy.” (Meaning that someone went all out or completely nuts over something or someone.)
“They’d bitch if you hung them with a new rope.” (Meaning the person would complain no matter what you did for them.)
This last one may be unique to where I grew up, being as I’m from Fort Smith, AR, home of Isaac Parker, “the hanging judge”. Supposedly if you hang someone with a new rope, it snaps their neck quickly, making the hanging as painless as possible. No, I’ve never tested this out, as I’m sure it’s damn difficult to convince the cops that it was all in the name of science.
[Foghorn Leghorn voice]Nice girl, but about as sharp as a sackful of wet mice[/voice]
I hate to be a wet blanket in this southern luuuuuv-fest but less than half of these colloquialisms strike me as the real McCoy. Anybody who’d stoop to using Foghorn Leghorn to press their point is dumber’n a sack of hammers… (Foghrn being voiced by Mel Blanc – undeniably talented – but born and bred in Californny.)
Like the plantation of Peckerwood from “Auntie Mame” it sounds plausible to ignit Yankee ears – but naw, y’all. Tain’t so.
Southern expressions are easily parodied, like Cockney accents, Midwestern naivete, West Coast counterculture New Ageisms, Far Right Wing Paranoia and African-American Ebonics. But y’all have got to learn the real thing. Hear?
Oops. I meant to add, “God bless her heart” to that crack about being dumber’n a bag of hammers. Danggone it, I done let something slip out the outhouse again.
A “mess” is also used to describe someone admiringly, especially a child. “That Caitlyn sure is a mess.”
The women in my family often exclaim, “Leroy!” when someone farts. Don’t know if that’s Southern, exactly, but they are. Poor Leroy needs to change his diet, if he’s been that gassy this long.
Well, it may be unique to Arkansas, but not necessarily to the western border; I mainly grew up in the eastern part of the state (Woodruff, Prairie, and Monroe Counties), but my dad said it all the time about my mom – or the variant “if you hung her with a silk rope” (which argues for the “new” bit being mainly about the quality of the material, not about any supposed advantage in making the process painless).