An overused alternative way of saying 'what the hell', made popular by Georgians who feel the need to act like a 'peach'.
The phrase you will hear when you catch a couple playing dirty (ie third basing it on a clearly visible outdoors bench). Also the same phrase you will have in your mind when you first see them performing the action, and the last words you will be thinking of before you throw up all over your new shirt.
"Dude what the heck, I heard you tell other people that I say 'what the heck' a lot." What the heck.