You know a line I think should be outlawed in all future movies and TV shows? This one: "You have no idea what i'm capable of." It's usually spoken in a low, tough-guy sort of voice, and can either be by the good guy or the bad guy. But it's always a lousy writing device. Why does any character, EVER, need to say that to any other character? It's a cheap way to say to the audience, "Wait, don't walk out of the theater/change the channel yet. This guy gets more interesting later!" It's intended to create a sort of ambiguous menace and mystique around a character when they can't find a way to just give him a mystique the honest way.
Recent sightings include the first episode of the new show The Cape and the trailer for the new movie I Am Number Four. (That's not to say I didn't sorta like both otherwise...)
According to a quick Google search, it's also been used in the movies The Dark Knight and The Hulk.
But my favorite usage of the phrase comes as a quote of yet another usage thereof:
Got any other sightings of this phrase for me?