Well, some will say it's the nuclear reactor that provides power, others will say it's the torpedo tubes so they can defend themselves, and others will say it's the main engines that carry them to safety.

They're all wrong. The most essential piece of gear aboard a nuclear powered submarine is the ice cream machine. Submarines have a soft-serve ice cream machine that typically serves vanilla or chocolate ice cream—and that's one piece of critical gear that everyone agrees better stay working the entire deployment.