Director - James Cameron

Chaos and confusion are everywhere after the first attack by the xenomorphs decimate the Space Marines and their drop ship crashes. As the crew tries to get their bearing and fully understand what just happened, Private Hudson (Bill Paxton) - ever the pessimist - laments "That's it man, game over man, game over! What are we going to do now?"
The original line didn't include the "game over" part and was ad libbed by Paxton.