Victim: Joan Rivers
Date: August 24, 2012

Ouch. After Rihanna's Oprah Winfrey special where she talked about her relationship with Chris Brown, Joan Rivers made a typically Joan Rivers joke. Rihanna tweeted back: "@Joan_Rivers wow u really do get slow when you're old huh?" It was quickly deleted and she subtweeted about how Joan Rivers is so old she needs a diaper. Not Rih's best, but certainly up there.