And, of course, this scene from The Thing (1982) …
https://www.youtube.com/watch?v=EX9ZpsEg6Mc
They just don't make films like this anymore.
Dr Copper got both his forearms bitten off by the 'Norris-Thing'. An actor who was a double amputee was hired to play a screaming, mortally-wounded Dr Copper, wearing a Dr Copper face mask. It works because director John Carpenter cut away from it quickly.
Also, a special mention must go to the special effects, created by Rob Bottin. His effects should've gotten an Oscar - as it was, he wasn't even nominated. <--- ridiculous!