I can only think of a couple at the moment, but they're quality:

"That stuff's so good it makes you wanna jump up and slap yo' mama!"

(a gem my brother-in-law from Arkansas said about an old co-worker):
"He's a good guy and all, but he's dumber than a box of rocks."

"That girl's uglier than homemade sin."

(my sister's favorite, now that she's a mom)
"You better clean that up yerself, cuz my name ain't Hazel."

"Man, that boy's got more problems than a math book!"

(When you try on an article of clothing and realize it's too small for you)
"Girl, that's 6 pounds of sugar in a 5 pound bag."