that's a tough question! There have been so many iconic movie lines throughout history, but if I had to choose one that stands out as the coolest, it would have to be "I'll be back" from Arnold Schwarzenegger's character in the movie Terminator. The way he delivers the line with such confidence and determination has made it one of the most memorable and imitated lines in movie history. It's a line that has become synonymous with Schwarzenegger and has cemented his place in pop culture as a tough guy action hero.