7. Fight Scene, Rocky IV
This fight scene was so brutal that it was actually life-threatening: Sylvester Stallone and Dolph Lundgren were shooting a boxing scene, until Lundgren hit Stallone one time too many. "...After the third take of taking body blows, I felt a burning in my chest, but ignored it...", Stallone told Ain't It Cool.
"[Turns out] he struck me so hard in that my heart slammed against my breastbone and began to swell[...] and without medical attention the heart would’ve continued to swell until it stopped".
