My eye! Tell me another one! Get away with you! --> I would say that these are very old fashioned now. In a pig's eye! Get along with you! --> I've never heard of these ones personally (the second one just sounds like an unnatural version of "Get away with you!" though). Come off it! --> This one isn't bad I guess but isn't so common in my opinion. Here are some more common (and modern) examples: "No way!" "Really?!" "You're kidding!" "Are you joking?!"