At a recent Rihanna concert, one fan thought that it would be a good idea to grab RiRi as she made her way through the crowd. That was not such a good idea because Rihanna went into attack mode, with her microphone, when the overzealous fan wouldn't let go of her. 

Watch Rihanna unleash on this poor fan and its all caught on camera. Not sure if the fan sustained any injuries in this incident, but if they did, at least they can say that they were beat down by Rihanna. Lesson learned here, don't mess with Rihanna, girl has a quick swing.