Sarcasm
Oh yeah, you're really funny. (Actually you are, but you're so sarcastic that it's hard to tell when you're joking.) You mean what you say, but almost never say exactly what you mean. In fact you usually say the exact opposite. For instance, if your friend is wearing an ugly watch, you might tell them, "I wanted a watch like that once, but I got the wrong Happy Meal." Yep, there's a slight edge to your humor, but all you are really doing is telling it like it is, only like it's not.
Whether you're roasting a friend or playing social critic, your deadpan delivery and dry cynicism go a long way to expressing your true feelings...and making people laugh along the way.