Leonardo Di Caprio isn't often cast in supporting roles, but when Quentin Tarantino assigned him one in Django Unchained, he seized the spotlight in an unexpected way. When his sadistic plantation owner Calvin Candie loses his rag during that climactic dinner, he slams his fist on the table in anger, smashing it straight through a glass along the way.
In the screenplay, there was no glass involved, so the wound Di Caprio suffered was entirely genuine, as was the blood which spouted from it. Tarantino kept it in the final cut because he would have been a fool not to.
The actor never breaks character despite having glass embedded in his fist, and the moment he pulls the shards out afterwards is a nice touch.