Gesture: Hook 'em horns
What you think it means: "Rock on!"
What it means in Italy, Spain, Portugal, Brazil, and Colombia: "You're so dense you don't realize your wife is cheating on you". Often done behind a guy's back rather than to his face, this gesture's a popular insult at soccer matches. Now, sadly, "Go Horns, Beat OU!" is forever tainted in your mind.