The sign of the devil
is also employed as a symbol of something being "badass
". It is often made at rock concerts by hordes of angry young males.
Y'see, the devil sign is made by extending the pinky and index finger from a closed fist, with the palm facing away from you. The young men do this—often while screaming and making scary faces to the nearest camera—but they mistakenly extend the thumb as well. With the thumb extended, the super badass devil sign becomes the American Sign Language sign for "I love you." Hence, you now have a sea of angry waving hands all proclaiming their undying love.
This has a special sort of irony.