Others:
It's come a cloud. (meaning it's going to storm)
Well, bless her heart! (usually reserved for someone who did something mighty stupid)
Well, shit far! (meaning "fire", but pronounced "far" -- usually used when something bad has happened that is as unpleasant as the aftermath of eating beans or having diarrhea).
Go pick a switch! (meaning "uh-oh", we're not gonna get outta this)
That dog won't hunt. (meaning don't try to fool me)
I don't cotton to that. (I don't like it one bit!)
Don't trip on that bottom lip. (meaning, "Stop pouting")
He's/She's gonna bust a gut! (meaning, "He's/She's pissed and we're all gonna hear about it!")