Angel Matos was representing Cuba in taekwondo, the bronze final. His opponent was "Arman Chilmanov" from Kazakhstan. Here's the video of Angel Matos kicking the referee right in the face! This happened in Beijing 2008.
The Swedish referee "Chakir Chelbat" disqualified him for breaking a rule. It was then Matos gave him a kick to the face.
Note: I do NOT own the rights of this video!